Air-cooled information processing apparatus having cooling air fan, sub-fan, and plural separated cooling air flow channels

An air-cooled information processing apparatus has a plurality of units and a casing accommodating the units. At least one cooling air supply section and at least one cooling air discharge section are provided in the casing, for supplying cooling air into the apparatus and for discharging the air therefrom. A partition member divides the space inside the casing so as to define at least two cooling air flow channels between the cooling air supply section and the cooling air discharge section. At least one main fan unit is disposed in each of the cooling air flow channels. The cooling air flow channels include at least one first cooling air flow channel in which at least two units from among the plurality of units are disposed in parallel with each other with respect to the direction of flow of cooling air, and at least one second cooling air flow channel in which at least two units from among the plurality of units are arranged in series to each other along the flow of cooling air. This cooling arrangement ensures optimum cooling for different types of units in the apparatus, without being accompanied by rise in the noise level, rate of discharge of air, power consumption and production cost.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an information processing apparatus having 
a function of processing and storing information such as a computer, a 
filing device, a communication control unit and a channeling unit, and 
more particularly, to an air-cooled information processing apparatus 
forcedly cooled by air. 
The present invention also relates to a cooling structure for electronic 
apparatus, suitable for cooling an electronic circuit board loaded in an 
electronic unit, and more particularly to a cooling structure for local 
cooling of electronic apparatus using an improved slit jet duct. 
2. Description of the Related Art 
Generally, an information processing apparatus is composed of a casing 
which accommodates various units such as a central processing unit (CPU), 
a substrate equipped with LSI chips such as memory, a storage unit and a 
power supply. These units generate heat when operating. In general, 
operating temperature ranges, i.e., temperature specifications, are 
determined for this type of electronic unit. It is, therefore, necessary 
to cool inside the casing in order to maintain the temperature inside the 
casing within the temperature range determined by the specifications. In 
particular devices or units such as CPUs, semiconductor integrated circuit 
devices, hard disk-type storage devices and so forth require specific 
consideration in regard to cooling, in order to maintain the operation 
temperatures within optimum ranges which are generally limited in these 
devices or units. 
An information processing apparatus may be cooled by a water- or 
air-cooling method. The former needs a water supply, drainage equipment, 
pipes, heat exchanger and pump, etc. Thus, water-cooled apparatus involves 
problems or shortcomings such as greater scale of the apparatus itself, 
necessity of a large space required for installing a heat exchanger, etc. 
even within the apparatus to be cooled, risk of accidents such as leakage 
of cooling water, and necessity of protective maintenance for preventing 
such an accident. Necessity of water supply and drainage functions 
restricts the installation and impairs the mobility of the whole 
apparatus. In contrast, in the air-cooling method, there are no such 
problems. Therefore, in recent years, there is an increasing demand for 
air-cooling systems even in relatively large capacity information 
processing apparatuses such as those larger than workstations. 
Generally, an air-cooled apparatus has a cooling air inlet and an outlet 
provided in a wall of a casing, and a fan arranged on either the inlet or 
the outlet. 
Cooling in this air-cooled apparatus is performed by driving the fan which 
induces flow of air into the casing to cool the internal units and 
exhausts the air outside the casing. 
Arts concerning air-cooling of information processing apparatuses are 
disclosed in, for example, Japanese Unexamined Patent Publication Nos. 
63-108800 and 2-82693, as well as in Japanese Unexamined Utility Model 
Publication Nos. 62-10495 and 1-157492. More specifically, Japanese 
Unexamined Patent Publication No. 63-108800 discloses a cooling system in 
which the interior of the casing forms a portion of a cooling air channel, 
while Japanese Unexamined Patent Publication No. 2-82693 discloses an art 
in which suction means and a draft fan are provided for causing cooling 
air to flow between the exterior and interior of the casing, and partition 
walls are provided in the casing to cause the air to shunt and cool the 
internal units. Japanese Unexamined Utility Model Publication Nos. 
62-10495 and 1-157492 disclose cooling arrangements in which a circuit 
board as a source of heat is cooled by a cooling fan which is provided 
upstream of a package in which the circuit board is packaged. 
Current information processing apparatuses employ greater numbers of 
components or units than ever to meet the demand for diversification of 
functions. It is also a current trend that, in order to attain higher 
performance of the apparatus, circuit elements such as semiconductor 
integrated circuit devices are densely arranged on a board of a given 
size, resulting in a greater rate of generation of heat. Furthermore, 
current information processing apparatuses are required to deal with 
greater quantities of information and, hence, to have storage devices of 
greater storage capacity. Such storage devices of large storage capacity 
is realized by, for example, a disk array incorporating a multiplicity of 
hard disk devices. In order to improve the reliability of the whole 
information processing apparatus, these hard disk devices are kept under 
strict operation temperature specifications. 
Known forced air cooling techniques could meet these demands only by 
increasing the number of cooling air fans or by replacing existing fan 
units with a fan having greater power so as to increase the flow rate of 
the cooling air. 
These countermeasures are unsatisfactory in the following respects: namely, 
increase in the number of fans or replacement of the fan with a fan having 
greater power raises the level of noise, while increasing electrical power 
consumption and production cost, as well as the rate of air discharged, 
thus impairing the office environment. In addition, no specific 
consideration is given in the known countermeasures to the relationship 
between the pattern of flow of cooling air inside the apparatus and the 
temperature specifications of the unit to be cooled. Consequently, 
insufficient cooling occurs at local portions of the apparatus. Such local 
cooling insufficiency may be eliminated when the number of fans is further 
increased. The use of a greater number of fans, however, enhances the 
aforesaid problems such as increase in the noise, power consumption, cost 
and rate of discharged air. 
Japanese Unexamined Patent Publication No. 61-85899 discloses a cooling 
system for cooling electronic devices in which electronic circuit boards 
or devices as heat generators are encased in a casing and are 
simultaneously cooled by a cooling air fan which is so arranged as to 
generate flow of cooling air across the group of electronic circuit boards 
from front to rear side or from upper to lower side of the group of the 
electronic circuit boards. 
Japanese Unexamined Patent Publication No. 64-28896 discloses another 
cooling system which is suitable for use in the case where there are 
electronic devices which produce at different rates. This cooling system 
employs, in addition to a common air cooling arrangement using a common 
fan, a specific arrangement for concentrating cooling air to electronic 
devices which generate heat at large rates. Such a cooling air 
concentration means is usually realized by a duct which covers almost the 
entire area of the electronic circuit board to be specifically cooled, and 
jetting cooling air against such an electronic circuit board from a nozzle 
or nozzles connected to the duct. 
The cooling system of the type disclosed in Japanese Unexamined Patent 
Publication No. 61-85899, which employs a common cooling arrangement for 
cooling a plurality of electronic devices regardless of the heat 
generating rates, exhibits only a low cooling efficiency because certain 
portion of the cooling air is discharged without effectively taking part 
in the cooling. This cooling system, when applied to an apparatus which 
contains one or more electronic devices having specifically large rates of 
heat generation, requires that the rate of supply of the cooling air is 
increased to cool down such electronic devices, leading to increase in the 
noise of air in the fan and in the duct. 
The cooling system of the type disclosed in Japanese Unexamined Patent 
Publication No. 64-28896 also has a drawback in that large and complicated 
ducts are required to realize the cooling air concentration means and, 
therefore, could not suitably be used in concentrated air cooling of a 
plurality of electronic circuit boards or devices. 
Known information processing apparatuses, particularly those which are 
large in scale, employ front panels which are made of steel. Such a front 
panel is usually provided with peripheral tabs or flanges which serve as a 
reinforcer and which provide means for adapting the front panel to the 
apparatus casing. The peripheral flanges are effective in enhancing 
rigidity of the panel in longitudinal and breadthwise directions but 
cannot sufficiently stiffen the panel against distortion which may occur 
about diagonal lines. It is possible to stiffen the front panel by 
providing ribs on the back side of the panel or by increasing the 
thickness of the panel. Such countermeasures, however, are not recommended 
because the weight of the front panel is undesirably increased and hampers 
the handling of the front panel in protective maintenance work. When the 
front panel is supported for movement between open and close positions by, 
for example, a hinge, the increased weight of the front panel requires 
greater and stronger supporting structure. In addition, a front panel made 
of steel can have limited variation in the design due to inferior 
workability of the steel. Forming a large front panel with a resin 
requires a large mold, resulting in a rise in the production cost. 
Casings of electronic apparatuses such as computers or communication 
apparatuses generally have elongated box-like form in order to facilitate 
installation on a floor or in order to attain good harmonization of 
appearance with other apparatuses. The casing is usually composed of a 
box-like casing body and a thin front panel which covers the open front 
side of the box-like casing body, in order to meet requirements from the 
view point of ease of maintenance and design appearance. 
In most cases, the casing body is formed by sheet work from steel sheets in 
order to attain required strength and shield against electric wave. The 
front case is molded from plastics in the case of small-sized apparatuses, 
whereas, in large-size apparatuses, the front panel is formed by sheet 
work from a steel sheet. 
In a cooling system having a single flow path of cooling air, the air is 
made to flow along various complicated channels according to flow 
resistances posed by different devices or components in the computer 
casing. Consequently, insufficient cooling, as well as excessive cooling, 
takes place at various local portions in the computer casing, so that the 
whole cooling system exhibits inferior cooling efficiency. Cooling systems 
also are known in which independent cooling means such as fans are used 
for different heat-generating components. Cooling systems of this type 
suffer from disadvantages such as rise in the cost due to use of many 
fans, as well as complication in the construction of the cooling system 
and increased level of noise. 
In order to overcome these problems, a technique is disclosed in, for 
example, Japanese Unexamined Patent Publication No. 2-82693, in which an 
electronic apparatus such as a computer is cooled by air which flows 
through multiple paths. This technique, however, employs a suction means 
and a fan which causes flow of air between exterior and interior of the 
casing, and partition walls are provided in the casing so as to define 
multiple paths. This known technique therefore is still unsatisfactory 
from the view point of reduction in the noise level and improvement in the 
cooling efficiency. Various other techniques also have been proposed in 
regard to cooling of electronic apparatuses. For instance, Japanese 
Unexamined Patent Publication No. 63-108800 discloses an art which uses a 
double-walled casing. Japanese Unexamined Utility Model Publication Nos. 
62-10495 and 1-157492 disclose an art in which a cooling fan unit box with 
slits is disposed upstream of a space between heat-generating boards. 
These known techniques, however, employ only one path of flow of cooling 
air through the casing or a cooling fan is integrated with the circuit 
boards by means of air guides, failing to meet the demands for lower noise 
level and higher cooling efficiency. 
SUMMARY OF THE INVENTION 
Accordingly, it is a first object of the present invention to provide an 
air-cooled information processing apparatus in which, using a cooling 
system of a limited capacity, devices and components in the apparatus are 
adequately cooled by forced air cooling, without being accompanied by a 
rise in the production cost while suppressing increase in the noise, 
discharge air flow rate and electric power consumption. 
It is a second object of the present invention to provide an air-cooled 
information processing apparatus in which, despite a dense arrangement of 
devices or units such as heat-generating boards, e.g., IC chips and LSI 
packages, hard disks, power supply units and so forth, these devices and 
units can be efficiently cooled to ensure high reliability of the whole 
apparatus without raising the level of noise. 
It is a third object of the present invention to provide a casing structure 
for electronic apparatuses in which the rigidity of a front panel is 
enhanced to reduce distortion, while enabling divesification of the 
design. 
It is a fourth object of the present invention to provide an electronic 
apparatus cooling structure which has a simple construction occupying only 
a small space and yet capable of providing a high cooling efficiency while 
enabling local concentration of cooling effect to portions where 
electronic devices having specifically large rates of heat generation are 
installed. 
In order to achieve the first object, according to one aspect of the 
present invention, there is provided an air-cooled information processing 
apparatus having a plurality of units and a casing accommodating the 
units, comprising: at least one cooling air supply section and at least 
one cooling air discharge section provided in the casing; a partition 
member dividing the space inside the casing so as to define at least two 
cooling air flow channels between the cooling air supply section and the 
cooling air discharge section; and at least one main fan unit disposed in 
each of the cooling air flow channels; wherein, the at least two cooling 
air flow channels include at least one first cooling air flow channel in 
which at least two units from among the plurality of units are disposed in 
parallel with each other with respect to the direction of flow of cooling 
air, and at least one second cooling air flow channel in which at least 
two units from among the plurality of units are arranged in series to each 
other along the flow of cooling air. 
An assistant cooling device may be provided for enhancing cooling effect on 
at least one preselected unit of the units disposed in the first cooling 
air flow channel. The assistant cooling device may be a sub-fan for 
supplying cooling air to the preselected unit. 
The preselected unit may be a main processing unit including at least one 
processor, a group of memory devices, a plurality of boards carrying the 
memory devices and support members which support the boards in a 
substantially rectangular parallelepiped space. In this case, the sub-fan 
is disposed at the end of the main processing unit adjacent to the cooling 
air supply section. 
One of the units disposed in the second cooling air flow channel may be a 
storage device unit having a plurality of storage medium driving devices, 
disposed at an upstream portion of the second cooling air flow channel. 
The cooling air supply section may includes an outer wall portion having a 
first cooling air inlet and forming part of the outer wall of the casing, 
and an inner wall portion having a second cooling air inlet and spaced 
apart from the outer wall portion so as to define a channel therebetween; 
the first inlet and the second inlet do not overlap each other when viewed 
in the direction normal thereto. 
The main fan unit in the first cooling air flow channel may be disposed at 
the discharge end of the first cooling air flow channel. 
The main fan unit in the second cooling air flow channel may be disposed at 
the supplying end of the second cooling air flow channel. 
The suction port of the main fan unit of the second cooling air flow 
channel may be disposed downstream of the second air inlet of the air 
supply section, and a baffle member may be disposed in the space between 
the suction port and the second air inlet such that one of the suction 
port and the second air inlet is hidden behind the baffle member when 
viewed in the direction of flow of air. 
Part of the space between the inner wall portion and the outer wall portion 
of the air supply section may be filled with a silencing material. 
Although the first cooling air flow channel contains units which are 
arranged in parallel with one another, the invention does not exclude 
provision of any unit or units arranged in series to the parallel units in 
the first cooling air flow channel. Namely, the first cooling air flow 
channel may contain a plurality of units which are arranged in parallel 
and additional units which are arranged in series to such parallel units 
at the downstream side of the parallel units. Similarly, the invention 
does not exclude any parallel arrangement in the second cooling air flow 
channel, although the second cooling air flow channel has been described 
to essentially contain series connection of units. For instance, a pair of 
units which are parallel to each other may be disposed in series to 
another unit in the second cooling air flow channel. 
The casing accommodating a plurality of units has at least one air supply 
section and at least one air discharge section for supplying cooling air 
into and discharging the warmed cooling air from the interior of the 
casing. 
Thus, the space inside the casing communicates with the ambient air only at 
these portions. By minimizing the number of the portions which provide 
communication between interior and exterior, it is possible to suppress 
radiation of noise to the exterior of the casing, and to efficiently 
intake and discharge cooling air by fewer fan units. 
According to the invention, a member which materially forms a partition 
divides the space inside the casing so as to form at least two cooling air 
flow channels. At least one main fan unit is disposed in each cooling air 
flow channel. With this arrangement, it is possible to optimize the flow 
rates of cooling air along each cooling air channel. 
Preferably, the units arranged in parallel with one another within the 
first cooling air flow channel have cooling temperature specifications 
which are close to each other and which have comparatively small 
cross-sectional areas as viewed in the direction of flow of the cooling 
air. With this arrangement, the units can efficiently be cooled with fresh 
cooling air which is still low in temperature. 
In the second cooling air flow channel, units to be cooled are arranged in 
series along the channel. These units therefore are supplied with cooling 
air at an equal rate. Consequently, the units which are in a downstream 
portion of the channel receive cooling air which has been heated to higher 
temperature by the heat dissipated from the upstream units. Preferably, 
therefore, the units in the first cooling air flow channel are so arranged 
that the units which have lower upper limit temperatures and which require 
sufficient cooling are disposed upstream of units which have higher upper 
limit temperatures. With this arrangement, it is possible to efficiently 
cool the series units at moderate rates by a common main fan unit. 
It is possible to use an assistant cooling device for a specific unit or 
units out of the plurality of units so as to enhance cooling effects on 
such unit or units. The assistant cooling device may be, for example, a 
sub-fan which increases the velocity of cooling air directed to the 
specific unit or units so as to enhance the cooling effect. 
When the air supply section has a double-walled structure, it is possible 
to suppress direct external emission of noise generated by the fan inside 
the casing. 
The units arranged in parallel in the first cooling air flow channel may be 
stacked one on another. Similarly, the units arranged in series within the 
second cooling air flow channel may be stacked. Such a stacking of units 
makes it possible to efficiently dispose many units within the limited 
space inside the casing, while ensuring that cooling air is distributed to 
all these units. 
In order to achieve the second aspect, i.e., to realize an air-cooled 
information processing apparatus which can be efficiently cooled with 
reduced noise despite dense arrangement of units, the present invention in 
its another aspect provides an air-cooled information processing apparatus 
having heat-generating units such as IC chips and LSI packages, 
comprising: at least two cooling air flow channels through which cooling 
air flows to cool the heat-generating units; and a cooling air fan 
disposed in each of the cooling air flow channels, the cooling air fan 
being disposed between adjacent heat-generating units arranged along each 
cooling air flow channel. 
The second aspect of the invention can be realized in various ways. For 
instance, the cooling air outlet of each of the channels can be provided 
in the lower surface of the air-cooled information processing apparatus. 
In another form, the cooling air fan is disposed in each of the cooling 
air flow channels at a bend of the cooling air flow channel. The portions 
of the casing providing air inlet and outlet are preferably double-walled. 
It is also possible to provide an additional cooling air fan for the 
purpose of local cooling. 
It is also possible to arrange such that the circuit board itself form a 
part of the duct having restricted slit-like inlet and outlet, the outlet 
of the duct being disposed at the suction side of the cross-flow fan. 
The speed of the motor driving the cross-flow fan may be varied in 
accordance with the output of an air temperature sensor disposed in the 
vicinity of the suction end of the fan. 
The cooling air fan may be a commercially available through-flow fan. In 
such a case, the fan is arranged at a predetermined inclination. 
The CPU unit which is the core part of the apparatus may have a duct-like 
structure part of which is presented by an electronic circuit board. In 
such a case, a slide rail, lever and a guide pin are provided on the CPU 
unit. 
The hard disk device as data storage means may be constructed as a unit, 
with irregular spacing between adjacent hard disks. Such a hard disk unit 
is provided with a slide rail and a connector. 
Preferably, the air discharge port is provided in the bottom of an 
electronic device, and a punched member of 2 mm diameter, 4 mm diameter is 
provided in the air discharge port. 
It is also possible to use a common lever or separate levers as a jig or 
jigs for mounting and demounting the packages. Such jigs are preferably 
accommodated in the casing of the apparatus. 
The air supply section may have a dual port arrangement in which a pair of 
inlet ports are provided so as not to overlap each other. 
To achieve the third object, the present invention in its third aspect 
provides an air-cooled information processing apparatus having a casing 
including a casing body and a front panel which forms a front wall of the 
casing and which is made of a steel sheet, the front panel being recessed 
at its central portion leaving flat surfaces at both longitudinal ends 
thereof, the casing further including a resin mold part received in the 
recessed central portion of the front panel. 
The front panel may have a gate-shaped continuous flattened region 
including one longitudinal end portion and both lateral side portions of 
the front panel. The resin mold part may have such a curved surface that 
concaves at its central portion with both end portions flush with the 
front panel. It is possible to provide a decorative pattern consisting of 
convexities and concavities on the curved surface of the resin mold part. 
An indicating means may be provided on a flat surface which is presented 
at one longitudinal end of the resin mold part. 
At least the surfaces of the front panel and the resin mold part may be 
painted with achromatic colors of different color tastes. 
The resin mold part may have at least two small panels which are arranged 
side by side in the longitudinal direction. At least one of the small 
panels may be a bezel of a storage device. 
In a preferred form of the invention, the power storage battery is disposed 
in the vicinity of the bottom of the apparatus so that the weight center 
of the electronic device is set to a level below the level of the centroid 
of the whole apparatus. 
By using two or more cooling air flow channels, while adopting various 
measures such as installation of the cooling fan between adjacent 
heat-generating elements, disposition of the cooling air discharge port in 
the bottom of the apparatus, isolation of cooling fans from each other and 
double-walled structure of the casing, it is possible to effectively 
suppress the rise of air temperature inside the casing and to develop 
uniform temperature distribution over heat-generating units, thus reducing 
the power for driving the fans, as well as noise. 
Space factor inside the casing also can be improved by installing the 
cooling fans at the bends of two or more cooling air flow channels or by 
installing a commercially-available through-flow fan at an inclination, 
thus reducing the size of the casing and the production cost of the 
apparatus, while attaining excellent cooling effect. 
The invention can be carried out in various forms such as the use of a 
local cooling fan unit for cooling a unit which generates heat at a 
specifically large rate. It is also possible to arrange such that the 
circuit board itself forms part of the duct having restricted slit-like 
inlet and outlet, the outlet being disposed near the suction end of the 
cross-flow fan. It is also possible to construct such that the package 
circuit boards are arranged in the direction of flow of the cooling air 
through the duct. These arrangements offer effective supply of cooling air 
so as to ensure high degrees of reliability of operations of the devices 
or units such as the circuit boards carrying IC chips and LSI packages, 
hard disk device, power supply unit and so forth. 
The speed of the motor driving the cross-flow fan may be varied in 
accordance with the air temperatures sensed at the fan inlet by means of a 
temperature sensor of a control package. The speed control is conducted 
such that the speed of the fan is reduced when the sensed air temperature 
is low and increased when the same is high, so that wasteful supply of 
cooling air is avoided and the noise of the fan is reduced, thus attaining 
noise reduction of the whole computer apparatus. 
In the arrangement in which the CPU unit as the core part is constructed as 
a duct a part of which is formed of an electronic circuit board, it is 
possible to suppress temperature rise of the high-temperature portion of 
the CPU, thus contributing to improvement in the reliability of the 
semiconductors. In addition, demounting and mounting of the CPU unit can 
quickly be done by virtue of the slide rail, lever and the guide pin 
provided on the CPU unit having the duct-like structure. This permits an 
easy addition of the processing unit, as well as enhancement of the 
computing performance, thus providing an effective measure for maintenance 
and enhancement. 
In one form of the invention, the hard disk device as data storage means is 
constructed as a unit, with irregular interval between adjacent disks. A 
slide rail and a connector are provided on such a hard disk unit. This 
arrangement enables easy distribution of cooling air to the 
heat-generating elements downstream of the hard disk unit, while 
shortening the time required for demounting and mounting of the hard disk 
unit. It is therefore possible to add disks and to increase the storage 
capacity simply by replacing the hard disk unit. This arrangement 
therefore constitutes an effective measure for easy maintenance and 
enhancement. 
In one form of the invention, a punched member of 2 mm and 4 mm in diameter 
is provided in the air discharge port which is provided in the bottom of 
the electronic device. With this arrangement, the cooling air after 
cooling can be discharged from the entire area of the air discharge port, 
which decelerates velocity of the discharged air to eliminate generation 
of noise which otherwise may be caused due to collision of the discharged 
air with the floor, thus contributing to reduction in the noise. 
Common or separate levers as jigs for mounting and demounting the packages 
may be installed inside the casing of the apparatus. Such jigs shorten the 
time required for demounting and mounting, thus ensuring that the 
protective maintenance is carried out without fail. 
The air intake or supply port may have a dual hole arrangement having a 
pair of ports which are arranged so as not to overlap each other. One of 
these ports is provided in the panel cover. This arrangement effectively 
prevents direct emission of noise to the exterior from the interior of the 
electronic device. 
In a specific form of the invention, the weight of the power storage 
battery is so taken into consideration that the battery is situated near 
the bottom of the electronic apparatus at a level below the level of the 
centroid of the apparatus. This arrangement enhances the stability of the 
electronic apparatus to keep the apparatus upright even in the case of, 
for example, an earthquake. 
Furthermore, according to the present invention, a resin mold part is 
mounted in the central recessed portion of a front panel, thus stiffening 
the front panel against warp about diagonal lines. The resin mold part, 
which has a size smaller than that of the front panel, can have a variety 
of designs. 
It is possible to provide the resin mold part with a cushioning or bumper 
function. Any decorative pattern composed of convexities and concavities 
further enhances the strength of the front panel. 
The front panel and the resin mold part may be colored in achromatic colors 
of different color tastes. Such coloring of the front panel and the resin 
mold part provides good harmony between the apparatus and the environment 
in which the apparatus is installed, while eliminating necessity for 
consideration of discord of colors due to difference of colors between the 
steel sheet and the resin, as well as discord of colors between these two 
different materials which is enhanced due to difference in the rate of 
color degradation between these materials. 
In a specific form of the invention in which the resin mold part is 
composed of two or more small panels arranged side by side in the 
longitudinal direction, it is possible to reduce the size of the resin 
mold part and, by using the bezel of the storage means as one of the small 
panels, it is possible to obtain a plurality of types of apparatuses which 
are basically the same in construction but have diversified functions. 
In order to achieve the fourth object of the present invention, the present 
invention in its fourth aspect provides a cooling structure for cooling 
semiconductor devices in a casing by using a duct structure which has a 
plurality of slit-like openings. In a preferred form, the shapes of 
slit-like openings are varied corresponding to difference in the rate of 
heat generation between different units such as memory units. Uniform 
temperature distribution is obtained over many units such as memory units, 
by providing a local cooling fan in the duct or constructing the duct in a 
partly demountable manner. 
With the arrangement in accordance with the fourth aspect of the invention, 
it is possible to simultaneously cool a plurality of circuit boards. In 
addition, the duct can easily be mounted on and demounted from the casing. 
It is thus possible to obtain a cooling system which is quite useful from 
the view point of packaging. Variation in the shape of the slit-like 
openings in the duct makes it possible to supply cooling air at different 
rates to different semiconductor devices which generate heat at different 
rates, thus making it possible to cool the semiconductor devices to 
develop uniform temperature distribution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will be described with 
reference to the accompanying drawings. The overall structure will be 
described first followed by a detailed description. 
1. Overall structure 
An information processing apparatus embodying the present invention 
comprises the following components or units: a main processing unit 
including a high-speed RISC (reduced instruction set computing) processor 
with a cache memory, a main memory, a system bus connecting them and a 
controller; a storage unit having a plurality of hard disk storage 
elements; a communication unit; a power supply unit; and a cooling device, 
etc. 
A description will be given of the overall structure, beginning with 
illustration of configuration of the embodiment, followed by descriptions 
of the external structure of the casing and the mounting of units in the 
casing. 
1.1. System configuration 
FIG. 1 shows a system outline of a computer of one embodiment of an 
information processing apparatus according to the present invention. This 
embodiment comprises: a CPU package (CPU base board); a basic I/O 
controller 126 interconnecting and controlling a console 123 and RS 232C 
interface 124/centronics interface 125; a memory unit 5 (also referred to 
as an HDD unit) having a plurality of HDD (hard disk drive) devices 108 
arranged in an array therein; SCSI (small computer system interface) 
controller 132 interconnecting and controlling DAT (digital audio tape 
recorder) device 31, MT (magnetic tape recorder) device 130 and MCI 
(multiple communication interface controller) 131; and HPS (high 
performance server) bus 135 interconnecting and controlling ENA (Ethernet 
adaptor) 133 which is an Ethernet LAN (local area network) connect 
adaptor, FDDI (fiber distributed data interface) connect adaptor FAS (FDDI 
adaptor single attachment) 134, SCSI 132, ENA 133 and FAS 134. 
The CPU package 36 contains a high-speed RISC processor module 15 involving 
a cache memory, a mass main memory 17 for processing program and data, a 
system bus 120 interconnecting the RISC processor and various peripheral 
controllers; an MI (memory interface) 122 which is a controller of the 
system bus 120 and the main memory 17; an IOBC (I/O bus controller) 129 
connected to LAN 127 and CA (communication adaptor) 128 to control them; 
and BAs (bus adaptors) 140 connected to HPS buses 135 to control them. 
FIG. 2 schematically shows a logic of a CPU package 36, which is a main 
processing unit. The following components are mounted in the CPU package 
(CPU base board) 36: the RISC processor module 15, MS (main storage) 
middle card (memory module) 19, OSC (oscillator) package (OSC module) 16 
and BA package (BA module) 20, as well as the MCU (memory control unit) 
121, processor bus 136 and MI (memory interface) 122 controlling the 
system bus 137. 
The RISC processor module 15 has a high-speed RISC chip package 13 and a 
mass cache memory 14, and is connected to a processor bus of 8 byte/60 
Mhz. 
The MS middle card 19 has four blocks, each containing. Eight sheets of MS 
package 18 (memory sub module), and is connected to MCU 121. 
The OSC package 16 mounts a high-speed transmitting circuit and distributes 
clocks to respective modules. 
The BA package 20 is connected to a system bus of 8 byte/30 Mhz, and has 
IOBC 129 interconnecting and controlling the basic IO bus 138 and BAs 140 
interconnecting and controlling HPS bus 139. 
1.2 External structure of the casing 
FIGS. 3 to 6 are external views showing one embodiment of the computer of 
the present invention. FIG. 3 is a perspective view of a casing 1 of the 
computer. FIG. 4 is a front view; FIG. 5 is a rear view, and FIG. 6 is a 
right side view thereof. FIG. 7 is a perspective view showing an open 
condition of the front panel of the casing. 
The casing 1 has a main body 83 and a front panel 82. The front panel 82 
has a fixed panel 82a, a main door panel 82b and a sub door panel 82c. An 
indicator 104 is formed on the sub door panel 82c for indicating power 
supply and system running. The main door panel 82b and the sub door panel 
82c are formed such that they can move between open and close positions as 
shown in FIG. 7. A decorative panel 97 is fitted on the front portion of 
the main door panel 82b. As shown in FIG. 6, the decorative panel 97 is 
slightly protruded. 
FIG. 7 shows an open condition of the main door panel 82b and the sub door 
panel 82c of the front panel 82. When the sub door panel 82c is opened, 
operating portions of a control panel 106, a DAT 31, and 8 mm MT (cassette 
media tape recorder) 143 come out, and they can be operated therefrom. 
When the main door panel 82b is opened, a main breaker 107a of a power 
switch 107 and a charging breaker 107b come out. A computer 1000 can be 
accessed by switching them on. 
At the points of contact of the main door panel 82b and the sub door panel 
82c of the main body 83 with peripheral portions thereof, seize members 
83m are fitted. When the main door panel 82b and the sub door panel 82c 
are closed, these panels are locked by means of the seize members 83m. 
The main body 83 of the casing 1 contains an air supply panel 28 at the 
rear thereof, side plates 95 at both sides thereof, a top plate 94 at the 
upper surface, and a base plate 26 at the lower surface thereof. Air vents 
105 are provided in the air supply panel 28. The portion of the air vents 
105 of the air supply panel 28 constitutes a part of the inlet portion 
710, which will be described hereinafter. In this embodiment, the air 
supply panel 28 also serves as a cable cover. 
Skirt plates 26 and casters 25 are provided at the bottom portion of the 
casing 1. The skirt plates 26 are fitted over the entire surface of the 
front and both sides and a part of the rear surface. At both side portions 
of the skirt plates 26, air outlets 119 of, for example, 5 mm square are 
provided, to secure an air exhausting area. A punched member 27 having a 
lot of small holes is mounted on the air-outlet portion 750, as described 
hereinafter. 
In this embodiment, the casing 1 is an achromatic color of a gray shade 
which harmonizes with the installation. And, the color of the front panel 
82 and the main body 83 is different from the resin-molded portion 86 
adjacent to the front panel. Thus, the casing 1 harmonizes with the 
achromatic color used in many floors when viewed from a distance. 
Meanwhile, even though the casing 1 is colored differently in part, it is 
not necessary to consider the difference in a color of a steel plate and a 
resin placed adjacently, and due to differences according to the 
deterioration speed of the materials. 
As has been described above, according to this embodiment, magnetic 
shielding of the units inside the casing 1 can be obtained by forming the 
entire casing 1 with steel plate. 
Since the resin-molded portion 86 is fitted to a depressed portion 85 
formed on the decorative panel 97, the distortion of the front panel 
diagonally can be reduced. Therefore, the rigidity of the casing 1 can be 
obtained by lightening the weight of the front panel 82. 
Further, the casing 1 can be designed in various ways to down-size by 
miniaturizing the resin-molded portion 86. Therefore, various designs of 
the casing 1 can be obtained at a low cost. 
Still further, protruding the resin-molded portion 86 can provide a bumper 
function. Strength of the resin-molded portion and the decorative panel 97 
can be further improved by forming an irregular pattern on the 
resin-molded portion 86. 
1.3 Mounted structure 
The mounted structure of one embodiment of the computer of the present 
invention is shown in FIGS. 8 to 10. FIG. 8 is a perspective view showing 
the front of the computer 1000; FIG. 9 is a perspective view showing the 
rear of the computer 1000; and FIG. 10 is a plan view of the computer 
1000. 
The computer 1000 contains hardware resources having a system configuration 
as described above. It is assumed here that hardware resources are 
discrete components which can be handled independently. Thus, the computer 
1000 is regarded as having the following components: a main processing 
unit (CPU) unit 2 which is the heart of the computer; a basic I/O 
(input,output) package unit 3; a basic DC/DC converter 4a (FIG. 9); a 
storage unit (hereinafter also referred to as an HDD unit) 5 for storing 
information; an AC/DC converter 6 which is an electric supply portion and 
comprises a plurality of converters; cooling fan units 7a-7c which are 
cooling devices; a CPU backboard 8 which is an electric and signal 
intermediary unit; a HDD backboard 9; a circuit unit 118; an extended I/O 
(input, output) package 141; a cable cover 10 which is a sheath of the 
casing (FIG. 8); and a battery 11 as shown in FIGS. 8 to 10. Each of the 
HDD 108 of the storage unit 5 are fixed to the HDD backboard 9. 
The cooling fan units 7a-7c are dispersed and composed of the main fan 
units 7a and 7b serving as main fans, and the sub-fan unit 7c used for 
local cooling. 
Incidentally, units to be loaded can be suitably modified in accordance 
with the computer's specification. But, forms and sizes of the respective 
units and the positions thereof in the casing 1 should be determined in 
advance so that changing the position of the units in the casing 1 can be 
minimized even when the specification of the computer is modified. And, 
the cooling system need not be specially modified. 
From the viewpoint of mounting, the main processing unit 2 comprises, as 
shown in FIGS. 11A, 11B and 12, the following packages: an LSI package 12 
(MI 122, MCU 121 in FIG. 2) intermediating data exchanges between CPU and 
the memory; two sheets of RISC processor modules 15 equipped with an RISC 
chip package and a cache memory temporarily storing data; an OSC package 
16 controlling the active frequency of the RISC chip; four sheets of MS 
middle cards 19 consisting of a main storage; and a BA (bus adapter) 
package 20 intermediating different signal lines. This BA package 20 
contains a connector for transmitting electric signals to the extended I/O 
package 141. PA-RISC manufactured by Hewlett-Packard may be used as the 
RISC processor module 15 in the present embodiment. The MS middle card 19 
can mount a maximum of eight stages of an MS (main storage) package 18 
equipped with large memory capacity on both sides (see FIG. 42). 
1.3.1 Entire structure of the cooling system 
The entire structure of the cooling system for cooling units according to 
this embodiment will be described. 
A cooling system in this embodiment is arranged at every place in the 
casing 1 as shown in FIGS. 64 and 9, and has the following components: an 
inlet portion 710 for inducing cooling air; an outlet portion 750 for 
exhausting cooling air; two systems of cooling air flow channel, e.g. the 
first flow channel 730 and the second flow channel 740 both formed within 
the area from the inlet portion 710 to the outlet portion 750 by 
substantially separating an inner space of the casing 1 by a partition 
wall 760; a main fan unit 7a arranged in the first flow channel 730; and a 
main fan unit 7b arranged in the second flow channel 740. 
In the this embodiment, a plate-like member is used as the partition 760. 
However, the partition is not limited thereby. Any member may be used as 
the partition as long as it separates the flow channel. For example, side 
walls of the equipment, base board or the like may be used. Also, the 
partition may be omitted if the passage is substantially separated. 
A plurality of units is arranged in parallel along a flow of the cooling 
air in the first flow channel 730. Another plurality of units is arranged 
in series along a flow of the cooling air. That is to say, in the first 
flow channel 730, the cooling air blown into the casing 1 through the 
inlet portion 710 is separated to the respective units and blown out 
therefrom, combined to flow through the main fan unit 7a and exhausted out 
of the casing 1 through the outlet portion 750. In the second flow channel 
740, the cooling air blown into the casing 1 through the inlet portion 710 
flows along the respective units through a main fan unit 7b of an inlet 
720 and exhausts out of the casing 1 through the outlet portion 750. 
The respective units in the first and second flow channels may be arranged 
by temperature specifications thereof. Factors for determining the 
temperature specifications will be described hereinafter. 
The HDD unit 5 will be described first. In each HDD, a disk is rotated by a 
motor when it is actuated. The storage capacity of the HDD is proportional 
to the product of number of revolutions of the disk and the track's 
byte-average-speed (byte/sec). For example, the storage capacity of an HDD 
having 5400 revolutions and a byte average speed of 3.7 megabytes is 2 
gigabytes. Therefore, there is a tendency to increase the number of 
revolutions to increase the storage capacity of the HDD. Since the HDD 
constantly rotates at high speed on applying power, a bearing of the motor 
is heated. By a heat deformation of the bearing, a life of the HDD is 
shortened. Therefore, it has been found that the HDD has a severe 
temperature specification. 
In order to increase the calculating speed, it is necessary to lower the 
temperature of the semiconductor in the main processing unit 2 and in the 
main I/O package unit 3. For example, when the temperature of the 
semiconductor goes by 10.degree. C., the calculating speed increases about 
two times. When the temperatures of the respective loaded LSLs are 
uniformly distributed, reliability thereof is further improved. 
The conversion efficiency of the basic DC/DC converter 4a and AC/DC 
converter 6 are 78% and 85%, respectively. Upon conversion, these 
converters generate heat by 22% and 15%, respectively. However, since the 
AC/DC converter 6 has almost no semiconductors and generates no heat with 
respect to the operating temperature, it has not so severe temperature 
specification as other devices and packages. 
The air temperature near the circuit unit 118 may be increased by about 
5.degree. C. above the temperature of the main processing unit 2 and the 
basic I/O package unit 3 because power consumption of the circuit unit 118 
is low. 
Based upon the factors as described above, the upper limits of the air 
temperature are 50.degree. C. near the HDD unit 5, the main processing 
unit 2, the basic I/O package unit 3 and the basic DC/DC converter 4a, 
55.degree. C. near the circuit unit 118 and 60.degree. C. near the AC/DC 
converter 6. The upper limits of the surface temperatures of the 
semiconductors and the devices are 55.degree. C. at the HDD unit 5, 
85.degree. C. at the main processing unit 2 and the basic I/O package unit 
3, 70.degree. C. at the basic DC/DC converter 4a, 85.degree. C. at the 
circuit unit 118 and 90.degree. C. at the AC/DC converter 6. 
Accordingly, the cooling air flows in the main component as follows. In the 
first flow channel 730, the cooling air flows in the order of the inlet 
portion 710, (the main processing unit 2, the basic I/O package unit 3, 
the basic DC/DC converter 4a), the main fan unit 7a and the outlet portion 
750. In the second flow channel 740, the cooling air flows in the order of 
the inlet portion 710, (the bypass 711, the extended I/O package 141), the 
main fan unit 7b, the HDD unit 5, (the AC/DC converter 6, the circuit unit 
118), and the outlet portion 750. The units stated in the above 
parentheses are arranged in parallel as shown in FIGS. 8 to 10, 36, 64, 
65, 66 and 68. 
In the second flow channel 740, there is an extended I/O package 141 
between the inlet portion 710 and the main fan unit 7b. However, since the 
bypass 711 is in parallel, the cooling air from the portion 710 is sucked 
by the main fan unit 7b through the bypass 711. Therefore, even when the 
cooling air flows through the package 141, the temperature does not 
increase. The package 141 is the extended package and is sometimes 
omitted. However, since the extended I/O package 141 also serves as a 
sound insulation wall as described hereinafter, a dummy box or a package 
may be preferably arranged when the package 141 is omitted. 
The inlet portion 710 is a part of the outer wall of the casing, and has a 
dual structure of an outer wall portion 712 and an inner wall portion 713. 
The outer wall portion 712 is an air supply panel 28 provided with the 
first inlet 714 having a great number of air vents 105 within the 
rectangle (as also shown in FIG. 5). The box-shaped inner wall portion 713 
is fitted inside of the outer wall portion and is provided with the second 
inlet 715 arranged with a space for forming a flow channel of the cooling 
air. When seen from the rear side of the computer 1000 (FIG. 5), the first 
inlet 714 and the second inlet 715 are positioned not to overlap each 
other in order to prevent noises directly produced by the main fan unit 
7b, etc. (a top view is also shown in FIG. 62). 
A filter 29 is attached to the second inlet 715 to prevent dust from 
entering. Further, a silencing material 152 is fitted to a part of the 
inner wall portion 713. Glass wool having a thickness of about 15 mm may 
be used as the silencing material 152. The glass wool may be applied to 
the inner wall portion 713 with a double-sided tape or the like. 
The main fan unit 7a is arranged near the bottom portion of the inner side 
of a bottom plate 160 of the casing 1, at the exhaust side of the first 
flow channel 730. As shown in FIG. 36, the main fan unit 7a has a 
cross-flow fan 30. In the first flow channel 730, the cooling air is 
separated at the air supply side of the respective units such as the main 
processing unit 2, and each of the separated cooling air flows joins at 
the exhaust side thereof. The main fan unit 7a sucks in the joined cooling 
air and exhausts same through an opening 160a provided at the bottom plate 
160 and the outlet portion 750. 
According to UL standard, a punched member having punched holes of a 
diameter of about 2 mm or less is provided at an opening positioned below 
a heat source to prevent fire caused, one in a thousand, by sparks from 
the heat source having fallen on the floor. Also, the punched member 
having punched holes with a diameter of 4 mm is provided at the opening 
which is not positioned below a heat source to prevent small animals such 
as insects, rats or the like from intrusion. According to this embodiment, 
the punched member 27 having punched holes 27a with diameters of 2 to 4 mm 
is arranged at the surface of the outlet portion to meet the standard 
requirements as described above. By this, an air speed at the outlet 
portion 750 may be reduced. Further, the sound or the like generated when 
the cooling air 22 strikes against the floor may be extremely lowered. 
When the outlet of the cooling air 22 is arranged below the heat source, 
the cooling air should be exhausted outside the computer 1 through the 
punched holes having a diameter of less than 2 mm. However, when the 
cooling air 22 is exhausted through such small holes, a pressure loss may 
increase and a static pressure of the fan should be increased. Thus, there 
is a tendency of increasing of the load of the cooling fan, and of big 
noises. To improve this fact, the punched member 27 is made a box-shaped 
(irregular) to increase exhausting area. 
The typical forms of the punched member 27 are shown in FIGS. 36 and 68. 
FIG. 36 shows an example of the box-shaped punched member 27, and FIG. 68 
shows an example of the box-shaped punched member 27 having a protruded 
portion 27a on a portion thereof for increasing the opening area. 
Incidentally, as described hereinafter, a duct 33 is formed on the inlet 
side of the main fan unit 7a for dividing the cross sectional area of 
inlet 30b, as shown in FIG. 36. 
The main fan unit 7b is arranged on the inlet 720 of the second flow 
channel. As shown in FIG. 62, the unit 7b has two cross-flow fans 30, a 
case 721 for supporting the cross-flow fans 30 and a panel member 722 for 
constituting the inlet 720 at the front of the case. The panel member 722 
is provided with a great number of air vents 723 as shown in FIG. 50. The 
punched member may be used as the panel member 722. Such a panel member 
722 may be used for reducing a noise from the cross-flow fans 30. One 
object of using such panel member 27 is to reduce noises from the 
cross-flow fans 30. 
A shorter length of one cross-flow fan 30 than that of a vertical section 
of the passage is a reason of an arrangement of two cross-flow fan 30 in 
the main fan unit 7b. A shortage of length of the cross flow fans 30 may 
be avoided by arranging them at longitudinally different positions. 
The cross-flow fans 30 of the main fan units 7a and 7b are formed such that 
they can be driven at various speeds, and air speed may be changed as 
needed, as described hereinafter. As shown in FIG. 46, a control circuit 
as well as a temperature sensor 34 are mounted on any one of the packages 
of the basic I/O package unit 3 to change number of revolutions of the 
motor by an output signal from the control circuit. For example, when the 
temperature of the supplied air is 30.degree. C. or less, a voltage for 
driving the motor becomes 17 V, and 24 V when 30.degree. C. or more, 
thereby to change a volume of cooling air 22 from the cross-flow fan 30. 
1.3.2 Local cooling 
In this embodiment, in addition to the main cooling member in the first and 
second flow channels as described above, auxiliary units for particular 
units arranged in the first flow channel are provided in order to increase 
a cooling ability. As auxiliary units, sub-fan unit 7c is provided for 
blowing air to the particular units. Also, a duct 33 is provided as an 
auxiliary unit having a function of securing a volume of cooling air. 
In this embodiment, local and silent cooling is performed on the RISC 
processor module 15, the OSC package 16, and the basic I/O converter 4a in 
FIGS. 8 to 10. In the local and silent cooling, a heated portion at a high 
temperature (heat spot) is cooled at a minimum amount of flowing air by 
controlling the flowing of air in front and rear of the fan, thereby 
making it possible to cool a whole computer 1000 by a fan having a small 
cooling ability and generating smaller noise. The HDD unit 5 in the second 
flow channel 740 obtains a cooling effect almost same as that of the local 
cooling described above because it is positioned just after the main fan 
unit 7b. 
Cooling of the RISC processor module is described first. The cooling 
ability is increased by an individual forced air cooling method. For 
example, a board of PA 71000 series manufactured by Hewlett-Packard may be 
used for the RISC processor module 15. At least one sheet of the RISC 
processor module 15 is loaded in the main processing unit 2. In this 
embodiment, two sheets of the RISC processor modules are loaded in the 
main processing unit 2 as shown in FIG. 12. 
A structure of the RISC processor module 15 is shown in FIG. 11. One RISC 
chip package 13 is mounted on the RISC processor module 15 and twenties of 
cache memories 14 are mounted on both sides of the RISC processor module 
15. An electric signal may be transmitted by a male connector 49a. A 
disk-like radiating fin 62a is provided in the RISC chip package 13 for 
performing a sufficient cooling. 
FIG. 12 is a top view of the entire main processing unit 2. Two sheets of 
RISC processor module 15 and an OSC package 16 are arranged at one end 
portion (inlet side) of a case 190 of the main processing unit 2, and four 
sheets of MS middle cards 19 are arranged at the other end portion 
thereof. A sub-fan unit 7c for local cooling is formed outside of the end 
portion of the inlet side of the case 190. The OSC package 16 for 
controlling the RISC processor module 15 is formed adjacent to the RISC 
processor module 15. An axial fan 23a of 80.times.80.times.24 mm.sup.3 for 
supplying the cooling air 22, manufactured by Sanyo Electric Co., Ltd. and 
jet slits 24 are formed in the sub-fan unit 7c for local cooling. The 
axial fan 23a has a size of about 80 mm, a maximum flux of 1 m.sup.3, and 
a noise of about 30 dB. The jet slits 24 are formed rectangularly. 
Regarding a cooling of the RISC processor module 15, there is a problem of 
difficulty in cooling the cache memories 14 positioned at a lower portion 
of the disk-like radiating fin 62a. This problem is attributable to the 
fact that the cooling air from the axial fan 23a is slightly blocked by 
the disk-like radiating fin 62a (especially, by a post portion thereof) 
and that the cooling air is considerably warmed when passing through the 
radiating fin 62a. 
FIGS. 13A and 13B show a specific example of a cooling of the RISC 
processor module 15 according to the present invention. In the embodiment 
of FIGS. 13A and 13B, four rectangular jet holes are provided in the sub 
fan unit 7c for a local cooling. The RISC processor modules 15 may be 
cooled from the both side thereof because they are positioned between two 
jet slits 24. By this, flowing speed of the cooling air along a substrate 
may be increased and cache memories 14 behind the RISC chip packages 13 
may be sufficiently cooled. 
In this embodiment, positions of guide rails correspond to those of 
portions between the jet holes. Thus, flowing of the cooling air from the 
jet slits 24 is not interrupted by the guide rail 301. The size of the 
duct is 9 by 70 mm. 
In this embodiment, the RISC chip packages 13 and the cache memories 14 are 
designed so as to have temperatures sufficiently below the upper limit 
temperatures of 110.degree. C. The lower the operating temperature of the 
RISC chip packages 13 and the cache memories 14 become, the reliability 
thereof become more sufficient. It is known by experience that reliability 
and speed of calculation is remarkably increased when elements are used at 
a junction in a wiring board with a maximum temperature of 85.degree. C. 
or less, in comparison with a case when used near the upper limit 
temperature of 110.degree. C. 
Incidentally, in the embodiment of FIGS. 13A and 13B, the RISC processor 
module 15 may be cooled in a same manner as described above as long as the 
axial fan 23a is running even when the cross-flow fans 30 for cooling a 
whole of the computer 1000 stop. On the other hand, even when the axial 
fan 23a stops, a parallel flow of the cooling air is formed by the 
cross-flow fans 30 and the RISC processor modules 15 are operated at 
temperatures lower than the upper limit of 110.degree. C. Therefore, it is 
assumed that dual cooling is performed. 
In this embodiment, the axial fan 23a is provided at the upper side of the 
RISC processor modules 15. However, even when the axial fan 23a is not 
provided, cooling air direction may be controlled by providing a duct 103 
as shown in FIGS. 14A and 14B, and sufficient cooling ability may be 
obtained. 
One surface of the OSC package 16 formed adjacent to the RISC processor 
modules 15 is cooled by the jet from the axial fan 23a, and the other 
surface thereof is cooled by a parallel flow of the cooling air from the 
cross-flow fans 30. By this, the elements on the circuit board may be 
sufficiently cooled compared with the case when both surfaces of the OSC 
package 16 are cooled by the cross-flow fan 30. 
Further, this embodiment may be modified as shown in FIG. 15. An opening 
portion 103a of the duct 103 of the fan unit 7c for local cooling as 
described above may be extended up to the position of the OSC package 16. 
By this,the cooling air from the axial fan 23a may be supplied to IC chips 
fitted on the under surface of the OSC package. As a result, reliability 
of the OSC package may be increased. 
The modifications of cooling the RISC processor modules 15 will be 
described with reference to FIGS. 16 to 37. 
FIG. 16 shows a first modification. One or two circuit boards are provided. 
One CPU 313 and twenties of memories are mounted on the circuit board. A 
duct 303 is provided at an upper portion of the circuit board. An axial 
fan 23a is provided at a further upper portion of the circuit board so as 
to contact with the duct 303. An OSC board 2 for controlling a cooling of 
the circuit board is formed adjacent to the circuit board. 
Regarding a cooling of the circuit board, there is a problem of difficulty 
in cooling the memories 14 positioned at a lower portion of a disk-like 
heat sink 300. This problem is attributable to the fact that the cooling 
air from the axial fan 23a is slightly blocked by the disk-like heat sink 
(especially, by a post portion thereof) and that the cooling air is 
considerably warmed when passing through the heat sink 300. 
Accordingly, two large rectangular slits are provided in the duct 303 in 
the embodiment of FIG. 16. The respective centers of the slits 302 and the 
center of the substrate 1 are coaxially arranged. By combining the slits 
302 and the guide rails 301, four rectangular slits 302 are substantially 
formed. By this, speed of the cooling air flowing along the circuit boards 
1 may be increased and cache memories 14 behind the CPUs 315 may be 
sufficiently cooled. Since the respective slits 302 have sufficiently 
large width, the guide rails 301 have less effect on flowing of the 
cooling air from the rectangular slits 302. Thus, the embodiment has the 
following advantage: pressure loss of the duct 303 is small because of the 
wide width of the slits 302, thereby increasing a volume of the cooling 
air flowing from the axial fan 23a; and the cooling ability is not changed 
even when the relative position of the circuit board 1 and the duct 303 is 
slightly shifted. The size of the slits is 36 mm by 70 mm, and the slits 
are formed with the space of about 6 mm. The distance between the guide 
rails 301 and the duct 303 is about 2 mm. The pitch between the circuit 
board 1 is about 42 mm. The disk-like heat sink 300 has a disk having a 
diameter of 64 mm, a post having a diameter of 20 mm and a fin having a 
thickness of 1 mm, pitch of 4 mm and a height of 25 mm. 
FIG. 17 shows a modification of FIG. 16 in which the axial fan 23a formed 
as upper portion of the duct 303 by contact therewith is removed. 
FIG. 18 shows an embodiment in which three rectangular slits 302 are formed 
in the duct 303. Similarly to the embodiment shown in FIG. 16, the speed 
of the cooling air flowing along the circuit boards 1 may be increased and 
cache memories 304 behind the CPUs 315 may be sufficiently cooled. The 
size of the slits is 16 mm by 70 mm. The guide rails 301 may be removed 
from the embodiments shown in FIGS. 13 and 16. 
FIG. 19 shows an embodiment in which louvers are used. By bending the flow 
of the cooling air from the axial fan 23a with the louvers 305, the 
portion where it is difficult to cool the memories 304 may be locally 
cooled. This embodiment has advantage that the memories 304 provided at a 
lower portion of the heat sink 300 on the circuit board 1 may be 
sufficiently cooled. The size of the respective louvers is 10 mm by 70 mm, 
and angle thereof is about 30.degree.. FIGS. 20 to 22 show embodiments in 
which other slits having a different size is formed between the slits 302. 
The temperatures of the memories 304 behind the heat sink 300 loaded 
between the circuit boards 1 are apt to increase. In this embodiment, the 
memories 304 may be cooled by satisfactorily applying the cooling air 
thereto or by increasing the amount of the cooling air. 
FIGS. 23 to 30 show embodiments in which the slits are of various shapes, 
such as H-shaped, oval, diamond-shaped, I-shaped, cross-shaped and 
U-shaped or the like. 
FIG. 31 shows an embodiment in which the duct 303 of the CPUs 313 is 
box-shaped with opening front thereof. In this embodiment, the amount of 
cooling air is increased by reducing a pressure loss of the duct 303 at an 
exit thereof, and the cooling air from the axial fan 23a is applied to the 
circuit boards 1 without dispersing. This embodiment has advantage of 
simplification of structure of the duct 303. 
In the embodiments shown in FIGS. 18 to 31, the axial fan 23a is connected 
to the duct 303. However, as described in the embodiment shown in FIG. 17, 
sufficient cooling ability may be obtained by providing the ducts 303, 
even when the axial fan 23a is not provided. 
FIG. 32 shows an embodiment in which the duct 303 is not provided. The flow 
of the cooling air from the axial fan 23a is tightened by the guide rails 
301 and become an accelerated jet, thereby making it possible to disarray 
the flow of the cooling air and to perform cooling. This embodiment has 
advantage of simplification of the cooling structure. 
FIGS. 15 and 33 show embodiments in which the duct 303 is elongated to an 
OSC board 16 controlling the CPU. These embodiments have the advantage 
that the memories loaded on the OSC board 16 may be sufficiently cooled. 
FIGS. 34 and 35 show embodiments in which the disk-like heat sink 300 is 
replaced by a comb-like flat fin 300a or pin fins 300b. The memories 304 
or the like loaded on the circuit boards 1 may be sufficiently cooled even 
when the heat sink 300 is replaced. 
The axial fan 23a is connected to the duct 303 also in the embodiments 
shown in FIGS. 33 to 35. However, as described in the embodiment shown in 
FIG. 17, sufficient cooling ability may be obtained by providing the ducts 
303 even when the axial fan 23a is not provided. 
According to the cooling structure as described above, jet of the cooling 
air having almost uniform speed may be suitably applied only to the 
necessary portion in the form of a slit, while corresponding to calorific 
value or the like of the electric circuit board to be cooled. Thus, the 
cooling structure may exhibit the considerably excellent effects as 
follows: sufficient cooling efficiency may be obtained even with a 
relatively small amount of the cooling air, thereby to compact the cooling 
device; a space for the electronic units in the casing may be simplified 
and saved with almost no change of the casing structure; and concentrated 
cooling of the electric circuit board loading semiconductor elements 
thereon having large calorific value may be performed. 
In FIGS. 64 and 65, a divergent duct 741 is provided at the exit of the 
cross-flow fans 30 in the HDD unit 5 for applying the high-speed cooling 
air discharged from the cross-flow fans 30 uniformly and directly to the 
respective disks. By this, the respective disks are sufficiently cooled 
and succeed in obtaining thermal reliability same as that of the disks in 
a general large computer. 
A large amount of cooling air should be flown in the basic DC/DC converters 
4a. Thus, as shown in FIG. 36, the duct 33 is formed at the inlet 30b of 
the cross-flow fans 30, thereby to perform sufficient cooling. That is to 
say, the duct 33 is formed on the inlet side of the main fan unit 7a for 
dividing the cross sectional area of the inlet 30b. The duct 33 is formed 
for securing the amount of the cooling air to the basic DC/DC converters 
4a. The duct 33 is arranged along an axial direction of the inlet 30b of 
the cross-flow fans 30. Thus, the duct 33 divides the inlet 30b of the 
cross-flow fans 30 with an angle. In this case, the cross-flow fans 30 are 
not effected by the change of load balance. Therefore, generation of 
noises at the cross-flow fans 30 may be controlled. Meanwhile, when the 
axial direction of the cross-flow fans 30 is divided and load balance is 
changed at the axial direction of the cross-flow fans 30, rotation axes of 
the cross-flow fans 30 vibrate to generate noises. 
1.3.3 Operation of the cooling 
In this embodiment, as has been described above, a space in the casing 1 is 
divided into the first and second flow channels, and these channels are 
entirely cooled by the main fan unit 7a and 7b, respectively. Also, in 
this embodiment local and silent cooling is performed on the main 
processing unit 2, particularly on the RISC processor module 15, the OSC 
package 16 and the basic DC/DC converter 4a. 
The operation of cooling in the first and second flow channels will be 
described in detail with reference to FIG. 9; FIG. 62; FIG. 36 which is a 
cross sectional view taken on line XXXVI--XXXVI of FIG. 8; and FIG. 64 
which is a cross sectional view taken on line LXIV--LXIV of FIG. 8. 
The operation of the cooling in the first flow channel will be described 
first. The cooling air 22 flows into the casing 1 from the air vents 105 
of the inlet portion 710 formed at right half side of the air supply panel 
28 (located at this side and not shown in FIG. 36) behind the casing 1 
through the left half side of a inner cover provided with a filter (shown 
by broken lines) as shown in FIG. 9. Then, the cooling air flows through 
the side faces of the extended I/O package unit 141 and the main 
processing unit 2, a guide panel 739 covering a part of the basic I/O 
package unit 3 and the basic DC/DC converter 4a, and a space 719 formed 
between air supply panel 28 and the inner wall (see FIGS. 62 and 64). 
Further, a part of the cooling air 22 flows into the right side face of 
the casing 1 (left side surface seen from the behind). The cooling air 
flows into the casing 1 and is put in order by the guide panel 739 to flow 
almost uniformly toward opening portion of the units arranged in parallel. 
That is to say, by covering the rear sides of the basic I/O package unit 3 
and the basic DC/DC converter 4a with the guide panel 739, disordered flow 
of the cooling air into the basic I/O package unit 3 and the basic DC/DC 
converter 4a may prevented, thereby making it possible to guide the 
cooling air to the opening, as described hereinafter and to distribute in 
a fixed amount in accordance with the predetermined cross sectional area 
of the opening. Therefore, each of the units may be cooled properly by the 
fans having the restricted ability. 
The cooling air 22 flows to the main processing unit 2 through the punched 
hole of the opening 733 located at the end portion of the right side 
surface of the casing 1. Then, the cooling air 22 flows into inside of the 
main processing unit 2 from the axial fan 23a to flow horizontally along 
the circuit boards in the main processing unit 2 (see FIG. 12). 
The cooling air flowing near the guide panel 739 flows into the basic I/O 
package unit 3 and the basic DC/DC converter 4a through the punched holes 
formed in the openings 734, 735 and 737 of the guide panel 739 and the 
punched hole of the opening 738 formed at the end portion of the basic 
DC/DC converter 4a, and passes through between the circuit boards. 
The cooling air passed through the main processing unit 2, the basic I/O 
package unit 3 and the basic DC/DC converter 4a joins at a hollow 732 
formed above the cross-flow fans 30 and is drawn by the cross-flow fans 
30. After flowing out from the cooling fan unit 7a, the cooling air 22 
flows out from the air vent 27a of the punched member 27 formed in the 
opening portion 160a of the base plate 160 and passes under the skirt 26 
and the casters 25. And then, the cooling air 22 is discharged outside of 
the casing 1. 
The amount of the cooling air passing through the main processing unit 2, 
the basic I/O package unit 3, and the basic DC/DC converter 4a may be 
substantially determined by the cross sectional areas of the openings. In 
this embodiment, the amount is determined by the openings 733, 734, 735, 
736, 737 and 738. In other words, the size of these openings is decided 
for determining the amount of the cooling air to be flown into the units 
arranged in parallel. 
Accordingly, when developed cooling ability is required, it is necessary to 
provide the auxiliary units. In this embodiment, a sub-fan 7c is provided 
to the main processing unit 2 in order to increase the amount of the 
cooling air passing in the main processing unit 2, thereby to increase 
cooling ability. Regarding the basic DC/DC converter 4a, the duct 33 is 
provided thereto for securing the fixed amount of the cooling air. 
The operation of the cooling in the second flow channel will be described. 
As shown in FIG. 64, the cooling air 22 flows into the casing 1 from a 
right half side of the air supply panel 28, flows out from the left half 
surface of the inner cover provided with the filter 29 (shown by an arrow 
of a broken line) and flows into the extended I/O package unit 141. After 
flowing in the extended I/O package unit 141, the cooling air 22 is drawn 
by the cooling fan unit 7b. Also, after flowing into the casing 1 from the 
air supply panel 28, the cooling air is drawn by the main fan unit 7b 
through the bypass 711 (see FIG. 62). 
In the former case, the cooling air 22 is introduced from an opening 141x 
and 141y of the extended I/O package unit 141, flows obliquely or 
horizontally through the extended I/O package 141, and then is exhausted 
from an opening 141z formed at the lower side of the extended I/O package 
unit 141. In order to let the large amount of cooling air flow into the 
DC/DC converter 4a of the extended I/O package unit 141, inlet of the 
extended I/O package unit 141 to the DC/DC converter 4b is enlarged. 
In the latter case, after flowing out from the air supply panel 28, the 
cooling air is not introduced directly to the main fan unit 7b having two 
cross-flow fans 30 but is introduced near the rear portion of the extended 
I/O package unit 141. That is to say, the inlet portion 720 of the main 
fan unit 7b is only located near the rear portion of the extended I/O 
package unit 141, and is opened over the region of the extended I/O 
package unit 141. 
As shown in FIGS. 62 and 36, a silencing material 152 is attached by a 
double-sided adhesive tape to the region other than the area which 
overlaps the extension I/O package unit 141, so as to oppose the air 
supply panel 28. 
The flow of the cooling air 22 from the cross-flow fan 30 is deflected and 
the deflected air is made to pass through the diverging duct 741 and 
passes the HDD unit 5, AC/DC converter 4 and the circuit unit 118, so as 
to be discharged through the punched member 27 of the floor plate, as in 
the case of the first air flow channel 730. The air is then relieved to 
the exterior of the computer housing 1 via the discharge holes (small 
holes) in the skirt 26 and also through the space between the skirt 26 and 
the floor. 
The cross-flow fan 30 is speed-controlled in accordance with a control 
signal given from a control circuit board of the basic I/O package unit 3. 
Thus, the control circuit on the control circuit board of the basic I/O 
package unit 3 operates to control the fan motor speed in accordance with 
the output from a temperature sensor 34 connected to this control circuit. 
A description will now be given of the flow channel through the HDD unit 5, 
AC/DC converter 6 and the circuit unit 118, with reference to FIG. 67. 
FIG. 67 is a top plan view of the front half part of the computer 1 (cut 
at a portion above the HDD unit 5). The arrangement is such that the 
cooling air flows through the spaces between adjacent HDDs 108, through 
the main AC/DC converter 70 which is a part of the AC/DC converter 6, 
through the INPUT section 67 and through the space between the long 
package 148 and the half package 149 of the circuit unit 118. 
This cooling structure offers the following advantages. 
Firstly, by providing a pair of cooling air flow channels in the computer 
1, it is possible to lower the temperatures of heat-generating units in 
the computer, thus realizing more uniform temperature distribution over 
plural heat-generating units, as compared with the case where only one 
cooling air flow channel is used. 
Secondly, by providing a sub-fan upstream of the heat-generating unit which 
generates heat at a specific rate, it is possible to supply cooling air to 
such heat-generating unit at a specifically large flow rate, so that the 
coefficient of heat transfer between the cooling air and the 
heat-generating unit is enhanced to effectively lower the temperature of 
such a heat generating unit. Provision of independent sub-fan also reduces 
burden on the main fan, thus eliminating necessity for the use of 
large-capacity fan motor and, hence, averting from problems which are 
inevitable when large-capacity motor is used, such as increase in the 
noise, electrical power consumption and production cost. 
Thirdly, the installation of a cross-flow fan inside the casing 1 prevents 
external emission of noise which is generated inside the fan, as well as 
the noise generated as a result of collision of the air with an obstacle 
at the fan outlet, thus contributing to the reduction in the noise level 
emitted to the exterior of the casing 1. 
As the fourth point, it is to be noted that the skirt 26 provided on the 
bottom of the casing 1 remarkably reduces the noise which is generated 
when the cooling air 22 impinges upon the floor, while preventing dust and 
other matters from being scattered in the room. When discharge openings 
119 are provided in the skirt 26, air can be discharged not only from the 
bottom of the skirt 26 but also from such discharge openings. In other 
words, total cross-sectional area of the air discharge passage is 
increased, so that the pressure loss is reduced to enhance the cooling air 
flow rate. 
As the fifth point, the basic DC/DC converter 4a is supplied with cooling 
air at a sufficiently large rate, by virtue of the duct 33 provided in the 
discharge portion of the basic DC/DC converter 4a. 
As the sixth point, it is to be understood that the cooling air introduced 
into the second cooling air flow channel shuts into a portion which flows 
into the extension I/O package unit 141 and then into main fan unit 7b and 
a portion which is sucked into the main fan unit 7b composed of the pair 
of cross-flow fans 30 after being supplied from the air supply panel 28. 
This arrangement prevents excessive cooling air from being introduced into 
the extension I/O package unit 141. Consequently, pressure drop of the 
cooling air, as well as noise, can be reduced as compared with the case 
where all of the cooling air through the second channel is introduced into 
the extension I/O package unit 141. 
A seventh advantage resides in that the suction of the main fan unit 7b 
opens only at a region which confronts the extension I/O package unit 141, 
so that a large distance can be preserved from the air supply opening, 
while another region produces silencing effect by the provision of the 
silencing member 152. 
As the eighth point, it is to be appreciated that the duct 106 provided at 
the outlet portion of the main fan unit 7b produces a uniform pressure 
distribution of the air discharged from the fan, so that cooling air 22 is 
equally distributed to all HDDs 108, thus attaining uniform temperature 
distribution over the HDDs 108. In addition, reduction in the cooling air 
flow rate is diminished because the air is allowed to flow through the 
gaps between adjacent HDDs 108, through the main AC/DC converter 70, 
through the INPUT 67, and through the gap between the long and half 
packages 148, 149 of the circuit unit 118. 
Temperatures were measured at various portions of the apparatus in order to 
confirm the effect produced by the invention. As a result, it was 
confirmed that, when the temperature of the cooling air supplied is 
30.degree. C. or so, surface temperatures of the HDDs 108 around the 
bearings are generally 45.degree. to 47.degree. C., thus proving 
substantially temperature distribution over these HDDs 108. Meanwhile, the 
main processing unit 2 and the I/O package unit 3, which receive cooling 
air in parallel manner, exhibit a substantially uniform distribution 
ranging between 70.degree. and 80.degree. C. The temperature of the basic 
DC/DC converter is about 65.degree. C. which is sufficiently lower than 
the upper limit temperature. 
As the ninth point, it is to be noted that the rate of supply of the 
cooling air can be varied optimumly, since the speed of the motor for 
driving the cross-flow fan 30 can be changed in accordance with a change 
in the temperature of the cooling air, by virtue of the operation of the 
control circuit board of the basic I/O package unit 3. More specifically, 
when the temperature of the cooling air is high, the difference between 
the air temperature and the maximum allowable temperature of the unit such 
as semiconductor device on a circuit board is so small that increase in 
the flow velocity, i.e., flow rate, of air 22 is necessary in order to 
enhance the rate of heat transfer from the unit to the cooling air. 
Conversely, when the cooling air temperature is low, the above-mentioned 
difference in temperature is comparatively large, so that the flow 
velocity and, hence, the flow rate of the cooling air 22 can be set low. 
It is therefore not necessary to drive the fan motor at high speed when 
the cooling air temperature is low. Consequently, the motor 35 can sustain 
a longer use and the consumption of electrical power by the motor 35 also 
is reduced, resulting in reduced power consumption of the computer 1. This 
also eliminates the supply of wasteful or unnecessary supply of cooling 
air. At the same time, the noise of the computer 1000 also is reduced. 
As the tenth point,the air supply panel 28 on the rear side of the 
apparatus has a double-walled structure, and the air inlets formed in both 
walls are disposed so as not to overlap each other when viewed in the 
direction normal to these inlets. Consequently, the cooling air flow 
channel is bent or deflected to have increased length, thus producing 
silencing effect. A further silencing effect is achieved by attaching a 
silencing material 152 to the double-walled air supply panel 28 and the 
region other than the air inlet. The silencing material can be attached by 
mans of a double-sided adhesive tape so that it can be detached easily. 
A description will now be given of a practical example of the silencing 
effect produced by the invention. In general, it is known that information 
processing apparatuses of the same class as that of the invention exhibits 
a noise level of about 60 dB (A). The noise level is as high as about 55 
dB (A) even in rather "quiet" apparatuses. Even this low level of noise is 
annoying in an office and disturbs working environment in the office. It 
is to be appreciated that the invention achieves a considerable reduction 
in the noise level under such circumstance, as will be realized from the 
following description of the results of noise measurement. 
The measurement was conducted at a level which is half the height (height 
of casing plus 1 meter) at positions 1 meter apart from the respective 
walls of the casing and also at a position which is 1 meter above the top 
wall of the casing. The casing used in this embodiment had a height of 1.4 
meter, so that measurement was conducted at a level of 1.2 meter from the 
floor level, at four points which are 1 meter from the four walls of the 
casing. The measurement was first conducted without using the silencing 
material 152. In this case, the highest noise level of 48 dB (A) was 
obtained at the measuring point facing the air supply panel 28. The 
measurement was conducted again by charging the silencing material 152 at 
the position shown in FIG. 62. The highest noise level wa observed at the 
measuring point facing the air supply panel 28 also in this case, but the 
noise level was as low as 43 dB(A). The lowest noise level was obtained at 
the measuring point above the top wall, and the level of the noise at this 
point was as low as 40 dB. Noise levels at other measuring points were 
intermediate between these maximum and minimum levels. 
From these results of measurement, it is understood that the noise level 
can significantly be reduced in the embodiment as compared with the 
conventional arrangement, by virtue of the effect produced by the 
double-wall structure of the inlet portion 710 of the air supply panel 28 
with the inlet openings offset from each other so as to avoid direct 
emission of noise and by the effect of minimization of the number of the 
fans which are the sources of noise. It was also confirmed that the noise 
level can further be reduced by charging the silencing material. 
2 Constructions of Units 
Constructions of the units will now be described with reference to the 
accompanying drawings. Features mentioned in the foregoing description may 
be omitted from the following description in order to avoid duplication of 
explanation. 
2.1 Main Processing Unit 
FIG. 37 is an exploded perspective view and FIG. 38 is a perspective view 
of the main processing unit 2 of the computer 1000 embodying the present 
invention, illustrative of the manner in which the main processing unit 2 
is assembled, while FIG. 12 is a top plan view of the main processing unit 
2. 
The main processing unit 2 includes a CPU package as the main board, RISC 
processor modules 15 (two modules are used in this embodiment), OSC 
package 16, four MS middle cards 19, BA package 20, main case 37, front 
bracket 38, upper cover 39, slide rail 40, guide pin 41, setting guide 42, 
reinforcement plate 43, guide rail 44 and the lever 45. 
The main case 37 provides the back portion 37c and both side portions 37a, 
37b. A rectangular parallelopiped case 2a is formed by mounting, on the 
case 37, the main CPU package 36, the front bracket 38 and the upper cover 
39. That is to say, the main CPU package 36 and the main case 37 are 
fastened together by means of screws, and the front bracket 38 is screwed 
to the main case 37. After mounting the respective packages, the upper 
cover 39 is fastened to the front bracket 38 and the main case 37 by means 
of screws. 
Both side portions 37a, 37b of the main case 37 are constructed as to 
permit ventilation therethrough. Consequently, the case serves as a duct 
which has means of ventilation at its both sides. A local cooling fan unit 
7c is disposed on the side 37 of the main case 37, i.e., upstream of the 
outer RISC processor module 15 of the processing unit 2. The main 
processing unit 2 is provided with a multiplicity of guide rails 44 which 
are intended to facilitate insertion of the RISC processor modules 15, OSC 
package 16 and the MS middle card 19 into the main CPU package 36. In 
addition, as will be seen from FIG. 12, a rack member 37d for mounting the 
RISC processor modules 15, OSC package 16 and the MS middle card 19 is 
provided inside the main case 37. Guide rails 44 are laid between the rack 
member 37d and both sides 37a, 37b of the main case 37. The arrangement 
may be such that small holes are formed in both sides 37a, 37b and the 
rack member 37d so as to receive and retain lugs formed on both ends of 
the guide rails 44, thereby fixing the guide rails 44. 
As shown in FIGS. 38 and 12, a pair of guide pins 41 are secured to the 
back portion 37c of the main case 37 at the same level as each other by 
means of screws. 
The CPU package 36 has, as shown in FIG. 39, a setting guide 42 which is 
secured thereto. More specifically, a projection 47b on the setting guide 
42 is received in a small hole 46b formed in the main CPU package 36, 
thereby fixing the setting guide 42. 
The CPU package 36 also has levers 45 as shown in FIG. 37. These levers 45 
are rotatably mounted on both ends of the front bracket 38 of the main CPU 
package 36. 
Referring also to FIG. 40, a reinforcement plate 43 is attached to the back 
side of the CPU package 36 by means of screws 43a. In the illustrated 
embodiment, the screws 43a also serve to fix the main CPU package 36 and 
the main case 37, as will be seen from FIG. 40. 
FIG. 41 illustrates the manner in which units or devices are mounted on the 
CPU package 36. Units or devices such as an LSI package 12 for data 
exchange between the CPU and the memory are mounted on the CPU package 36. 
Female connectors 48a for connecting RISC processor modules 15, OSC 
package 16, MS middle card 19 and the BA package 20 are fixed by means of 
pins. The CPU package 36 has a board thickness of 2.7 mm and is composed 
of 12 layers. There are two levers 45 attached to both longitudinal ends 
of the CPU package 36. Male connectors 49a for connecting the CPU package 
36 to a CPU back board 8 are provided on other pair of longitudinal ends 
of the CPU package 36. Female connectors 48a have a multiplicity of signal 
pins, while the male connectors 49a are provided with holes for receiving 
these pins. 
FIGS. 11A and 11B show the manner in which elements are packaged on the 
RISC processor module 15. The RISC processor module 15 carries an RISC 
chip package 13 serving as the brain of the computer 1, and cache memories 
14 which serve as means for temporarily storing data. There are 13 cache 
memories on each side of the module 15. In order to increase the heat 
dissipation area, disk-like fins 62a are mounted on the RISC package 13 
through the intermediary of grease. Furthermore, male connectors 49a for 
connection to the main CPU package 30 are provided. In the illustrated 
embodiment an RISC processor module PA-RISC produced by Hewlett Packard is 
used as the RISC processor module 15. 
FIG. 42 illustrates elements or parts mounted on the MS package 18 and the 
MS middle card 19. There are eight female connectors 48f, two LSI chips 51 
and one male connector 49a on the MS middle card 19. To enable mounting 
and demounting, a pillar of a square cross-section of 5 mm wide/long is 
fastened by means of screws to the MS middle card 19 so as to be flush 
with the top edge of the MS middle card 19. The MS package 18 carries 
about 10 memory elements 18a on each side thereof. The MS package 18 has a 
male connector adapted to engage with the female connector 48f of the 
aforementioned MS middle card 19 so as to provide connection between the 
MS package 18 and the MS middle card 19. The MS package 18 serves as data 
storage means. Eight MS packages at the maximum can be mounted. This 
arrangement realizes a high-density three-dimensional packaging, allowing 
the cooling air 22 to flow through gaps between adjacent MS packages. It 
is therefore possible to make an efficient use of cooling air, thus 
achieving high cooling efficiency. 
FIG. 43 illustrates the manner of packaging of the BA package 20. The BA 
package 20 carries four LSI chips 53, and has four male connectors 49d and 
two female connectors 48. Three out of four male connector are used for 
mounting the BA package on the main CPU package 36, while the remaining 
one male connector and both female connectors are used for external 
control. The function of the BA package 20 is to relay different signal 
lines. In order to enable transfer of high-speed signals to other packages 
without reducing the signal speed, the central one 49d of the three male 
connectors 49d for connection to the main CPU package 36 is used as an 
input terminal, while two outer male connectors 49d are used as output 
terminals. The signals entering to the BA package are transmitted 
separately through four LSI chips 53. In order to prevent retardation of 
signal transmission, two LSI chips 53 on the left side and two LSI chips 
53 on the right side are mounted with 180.degree. inversion from each 
other. The BA package 20 is detachably mountable by using a lever action, 
with projections 47c of a hand lever 54 (see FIG. 44) inserted into small 
holes 46i formed in the BA package 20. 
A description will now be given of the manner in which the RISC processor 
modules 15, OSC package 16, MS middle card 19 and the BA package 20 are 
mounted on the main CPU package 36. Referring to FIG. 37, these packages 
are inserted into guide rails 44 secured to the main case 37. Then, male 
connectors 49 attached to the bottoms of the packages are inserted into 
female connectors 48 of the main CPU package 36 provided on the bottom of 
the CPU unit. Each female connector has a multiplicity of signal pins, 
while mating male connectors have holes for receiving these pins, thus 
providing electrical connection. The RISC processor modules 15 and the OSC 
package 16 are held by means of the guide rails 44, female connectors 48, 
male connectors 49 and the setting guides 42, while the MS middle card 19 
and the BA package 20 are held by means of the guide rails 44, female 
connector 48 and the male connector 49. 
FIG. 44 illustrates the construction of the hand lever 54. Mounting and 
demounting of the package is effected by lever action caused by the hand 
lever 54 which is brought into engagement with small holes formed in both 
ends of each package. A considerably high level of stress is generated in 
the CPU package 36 during mounting and demounting of the package. Such a 
stress, however, is effectively relieved by the reinforcement plate which 
backs up the CPU package 36, whereby the main CPU package 36 is freed from 
warp, thus ensuring high degree of reliability, as well as ease of 
maintenance. 
FIG. 45A shows the detail of the slide rail 40 illustrated in FIG. 37. The 
slide rail 40 has a male part 40a and a female part 40b. In order to 
ensure safety and reliability during attaching and detaching, a stopper 55 
is provided on the male part 40a. The female part 40b is provided with a 
hinge 56, in order to ensure safety and reliability of insertion of the 
male part 40a into the female part 40b. 
FIG. 45B shows an example of the mounting of the main processing unit 2 in 
the casing 1. A pair of the female parts 40b of the slide rails 40 are 
horizontally laid on a plate member inside the casing 1 and are fastened 
thereto by means of screws 781. A pair of male parts 40a of slide rails 40 
are laid horizontally on the main processing unit 2 and are fastened 
thereto by means of decorative screws 57. The mounting of the main 
processing unit 2 is conducted as follows. As the first step, the male 
parts 40a of two slide rails 40 are inserted into mating female parts 40b 
of the slide rails 40. The hinges 56 act so as not to allow the female 
parts 40b to be pushed back into the casing 1 until the male parts 40a are 
inserted into mating female parts 40b. When the male parts 40a have been 
inserted to midway, the stoppers on the male parts 40a start to act. 
Thereafter, the stoppers 55 are pushed so that the main processing unit 2 
can be inserted into the position of the CPU back board 8. 
Referring again to FIGS. 37 and 38, as the means for ensuring safety and 
reliability during mounting and demounting, as well as maintenance, of the 
main processing unit 2, a pair of tapered guide pins 41 are provided on 
the main case 37 substantially at the same level as each other, besides 
the slide rails 40 described above. The casing 1 is provided with small 
holes 46c at positions corresponding to the guide pins 41. The small holes 
46c have a size which is about 4 to 5 mm greater than the pins. These pins 
41 are received in the small holes 46c, whereby the main processing unit 2 
is held. Levers 45 are provided for the purpose of ensuring that the main 
processing unit 2 completely engages with the CPU back board 8. These 
levers 45 are rotatable in small holes 46d which are provided in both ends 
of the main CPU package 36 opposite to the ends which have the male 
connectors 49e. According to this arrangement, when the levers 45 are 
rotated until they are stopped by the plate member inside the casing 1, 
the male connectors 49e of the main processing unit 2 are brought into 
complete engagement with the female connectors 48e on the CPU back board 
48e, by the lever action of thee levers 45, thus achieving perfect 
connection between the main processing unit 2 and the CPU back board 8. 
Conversely, demounting of the main processing unit 2 from the casing 1 is 
conducted by rotating the levers 45 so as to disconnect the male 
connectors 49e from the female connectors 48e, so that the main processing 
unit 2 becomes extractable from the casing 1. When the main processing 
unit 2 has been extracted to midway, the user pushes the stoppers on the 
male parts 40a of the slide rails 40, so that the main processing unit 2 
can be detached from the casing 1. 
It will be understood that the described arrangement enables safe and 
reliable maintenance work. The male parts 40a of the slide rails 40 are 
secured by means of decorative screws 57 so that they can deviate 2 or 3 
mm, which facilitates insertion of the main processing unit 2. 
The main processing unit 2 has a duct-like structure, and the packages are 
arrayed in the same direction so as to enable cooling air to easily flow 
through the main processing unit 2. The CPU package 36 also forms part of 
this duct. The guide rails 44 for holding the packages and the metal 
plates are disposed at the air inlet and outlet of this duct. The side 
portions 37a, 37b of the main case 37 and the rack member 37d are provided 
with rectangular openings 58a which have shapes corresponding to the 
shapes of the respective packages. These shapes of the openings 58a are 
adopted so that the packages may be provided with cooling air 22 at 
different flow rates corresponding to the rates of generation of heat from 
the respective packages. In addition, the inlet area of the air of the 
duct is restricted to eliminate any wasteful portion of the cooling air 
22, while increasing the flow velocity of the cooling air 22, with the 
result that the rate of transfer of heat is increased to suppress 
temperature rise of the semiconductor elements on the package, thus 
improving reliability and performance of the computer. 
2.2 I/O Package 
FIG. 46 shows the detail of the basic I/O package unit 3 which is 
illustrated in FIGS. 8 and 9 and which embodies the present invention. 
The computer 1000 of this embodiment mounts 12 (twelve) basic I/O package 
units 3a in total. Seven out of the twelve are used for control of I/O 
device, while the remaining five are adaptable to BUS specification. An 
RPC (remote power on control) package is mounted as an option part. This 
package has a function of turning the power supply on and off through 
communication from the exterior. A power control package 3b and a package 
3c having the function of service processor are disposed under the basic 
I/O package 3a. The package 3c is provided with a temperature sensor 34 
and a control circuit which is not shown. This circuit board functions as 
a control circuit for controlling the motor which drives the cross-flow 
fan 30. Thus, the package 3c constitutes a control circuit board. It is 
possible to construct such that the sub-fan unit 7c also is controlled by 
this sensor and the control circuit. 
The four circuit boards positioned under the package 3c constitute the 
DC/DC converter 4a which will be described later. 
For mounting these packages, guide plates 59 of the packages are inserted 
into the guide rails 44. The guide rails 44 have projections inserted into 
the small holes in a metal plate inside the casing 1, whereby the guide 
rails 44 are fixed in the casing 1. The guide plates 59 are on lateral 
sides of the casing 1. After the insertion, the aforementioned hand lever 
54 is brought into engagement with the small holes 46f formed in both ends 
of upper part of each package, thereby driving the package into mount 
position by the lever action. After the mounting, the package is fixed at 
its both ends by screws to the metal plate inside the casing 1. In this 
state, the male connector on one side of the package is coupled to the 
female connector 48 on the back board, thereby enabling supply of 
electrical signals. A female connector 48 for GP-1B and RS232C for 
receiving signals from the exterior is provided on the portion of the 
package adjacent to the guide plate 59. 
A guide panel 73 (see FIG. 9) is disposed on the proximal side of the basic 
I/O package unit 3 and the basic DC/DC converter 4a as viewed in FIG. 46, 
so as to cover this side of the basic package unit 3 and the basic DC/DC 
converter 4a when they are mounted. 
The cooling air 22 passes through a constant-size chamber until it is 
sucked into the cross-flow fan 30 after flowing out of the basic I/O 
package unit 3. That is to say, the basic I/O package unit 3 forms a duct. 
Many semiconductor chips are mounted on each package. An I/O cover is 
mounted in the casing 1 so that the cooling air 22 is supplied from one 
side of the package and then through the package. The air discharge 
portion of each package has a rectangular opening 58b having a width equal 
to the width of the package, at a location other than a location where the 
guide rail 44b is provided. This arrangement ensures that whole cooling 
air 22 is supplied into the spaces between the packages,without being used 
wastefully. Consequently, the semiconductor chips mounted on the package 
can be effectively cooled to ensure high reliability of the apparatus. 
2.3 DC/DC Converter 
The basic DC/DC converter 4a used in the described embodiment is composed 
of a plurality of packages stacked in layers. The first and second 
packages as counted from the top are illustrated in FIGS. 47A, 47B and 
47C, while the third and fourth packages are shown in FIGS. 48A, 48B and 
48C. The conversion efficiency of the DC/DC converter 4a is 78%. Converter 
circuit boards are mounted on the packages of the basic DC/DC converter 
4a. More specifically, the first, second, third and fourth packages as 
counted from the top respectively mount two, two, one and two converter 
circuit boards 63. The upper three packages are formed of aluminum sheets 
64 so as to improve heat dissipation. In addition, the first and second 
packages as counted from the top have heat radiating fins 62a for 
increasing the area of heat dissipation, in consideration of the rates of 
dissipation of heat from the converter circuit boards 63. The heat 
radiating fins 62a have a length of 280 mm which is equal to that of the 
basic DC/DC converter 4a. The heat radiating fins 62a are constructed as a 
plate fin having seven fins integrally formed on a fin base plate. The 
width of this plate is 48 mm, fin height is 23 mm (base plate thickness 8 
mm) and the fin thickness is 3 mm. This fin plate can be formed by 
extrusion. In order to reduce contact heat resistance, a grease 65 having 
high heat conductivity is applied between the fins 62a and the aluminum 
sheet 64a, between the converter circuit board 63 and the aluminum sheet 
64a and between the aluminum sheet 64a and an aluminum sheet 64b which is 
secured to a metal plate inside the casing 1. The converter circuit board 
63, aluminum plates 64a, 64b and the heat radiating fins 62a are 
integrated by means of screws 64c. 
FIG. 49 illustrates the detail of an example of the practical construction 
in which the basic DC/DC converter 4a is mounted on the casing 1. The 
basic DC/DC converter 4a is inserted along the guide rails 44 so that the 
male connector 49 on one end of the basic DC/DC converter 4a is coupled to 
the female connector 48 on the CPU back board 8. Mounting and demounting 
of the basic DC/DC converter 4a is conducted in the same manner as those 
for the packages on the main processing unit 2 and the basic I/O package 
unit 3, using a hand lever 54 which is engageable with small holes 46h 
which are provided on both ends opposite to the connector. After the 
mounting, each package is fastened at its both ends to a metal plate in 
the computer 1 by means of screws. 
In order to effectively supply the basic DC/DC converter 4a with cooling 
air efficiently at a large rate, a duct 33 is provided to extend between 
the discharge opening of the basic DC/DC converter 4a and the suction side 
of the cross-flow fan 30. Since the base plate of the heat radiating fins 
62a extends in the same direction as the cooling air 22, it is possible to 
make an efficient use of the flow of cooling air 22, thus reducing the 
temperatures of the semiconductors and coils on the converter circuit 
boards 63a, 63b. The use of aluminum as the material of the converter 
structure improves heat conduction, thus contributing to improvement in 
the cooling performance, as well as to reduction in the weight of the 
computer 1000. 
2.4 Extension I/O Package 
FIG. 50 shows the packaging structure of the extension I/O package 141. The 
I/O package 141 carries, as is the case of the basic I/O package unit 3, 
12 (twelve) I/O packages and a DC/DC converter 4b which supplies power to 
the extension I/O package 141. The flow channel of the cooling air 22 is 
so set that the cooling air is taken from the left front side of the 
extension I/O package 141 and is discharged from the right rear side of 
the same so as to be sucked into the main fan unit. Packaging is conducted 
from the upper side and the power supplying DC/DC converter 4b is mounted 
on the uppermost stage. Heat radiating fins are provided on the reverse 
side of the DC/DC converter 4b. In order to increase the flow rate of the 
cooling air 22 into the power supplying DC/DC converter 4b, air supply 
opening is provided also on the left side, thus increasing the total 
cross-sectional area of the air inlet. 
According to the described arrangement, cooling air 22 is taken from the 
left front side of the extension I/O package 141 and is discharged from 
the right rear side of the same so as to be sucked into the cooling fan 
unit 7b, thus producing substantial cooling effect on the extension I/O 
package 141 which is provided with components such as connectors on both 
sides thereof. Since the packaging is commenced with the uppermost stage, 
and since this uppermost stage carries the power supplying DC/DC converter 
4b, it is possible to make an efficient and maximum use of the cooling air 
22 supplied by the cooling fan unit 7b. The power supplying DC/DC 
converter 4b exhibits improved heat dissipation by virtue of the heat 
radiating fins provided on the reverse side thereof, so that the 
temperature rise of this converter is minimized. 
2.5 Storage Unit (HDD Unit) 
FIGS. 51 and 52 show the detail of the HDD unit 5 in the computer 1000 
which was describe before in connection with FIGS. 8 and 9 as an 
embodiment. HDD 108 is fastened to an HDD plate 109 by means of screws, 
and the control signals and the power are connected to an HDD back board 9 
through a cable 109 between an HDD 108 and the plate 109. The male 
connector 49 fixed to the HDD plate 109 is fastened by means of screws and 
is supported by a floating type structure so as to be movable several mm 
to facilitate connection to the HDD back board 9. This floating type 
structure also produces an effect to prevent destruction of the HDD 108 
due to vibration. The male connector 49 is introduced while being guided 
by a guide pin 41 of a female connector 48 on the HDD back board 9. The 
HDD unit 5 is fixed to the casing by means of screws. 
According to the described arrangement, it is possible to smoothly load the 
HDD 108 and to improve reliability of the solder portion of the male 
connector 49 on the HDD 108 because the vibration of the HDD is 
sufficiently damped before transmitted to the HDD back board 9. 
FIG. 52 is a top plan view of the HDD unit 5. As will be seen from the 
drawings, the clearances 100 between the HDDs 108 are almost equal. By 
providing a diverging duct on the discharge side of the cooling fan unit, 
i.e., the air inlet of the HDD unit 5, it is possible to uniformly 
distribute the cooling air over the entire part of the HDD unit 5. 
Provision of an HDD back board 9 eliminates the necessity for the cable 
which is to be used for the purpose of signal transmission, whereby the 
construction is simplified considerably. In addition, since the disks are 
incorporated in the form of a unit, it is possible to replace the disks 
with smaller ones, e.g., to replace 5 inch disks with 3.5 inch disks, 
according to the user's specification. Thus, the described embodiment is 
effective also as an enhancing means. In addition, the described 
arrangement permits connection and disconnection of alive lines even 
during operation of the computer 1000. 
2.6 AC/DC Converter 
The AC/DC converter 6 has a single INPUT section 67, three main AC/DC 
converters 70 and a single auxiliary AC/DC converter. Two AC/DC converters 
70 are arranged on the upper stage, and one AC/DC converter 70 is set on 
the lower stage, as viewed from the direction normal to the plane of FIG. 
8. The power factor is 85%. The auxiliary AC/DC converter 74 is installed 
on the center of the lower stage as viewed in the above-mentioned 
direction. 
The construction of the INPUT section 67 is shown in FIGS. 53A, 53B and 
53C. The INPUT section 67 is disposed on the central lower stage as viewed 
in the direction normal to the plane of FIG. 8. The INPUT section 67 is 
supplied with electrical power of A.C. 200 V through a three-layered power 
supply cable connector. A breaker 68a is provided on an upper part of the 
INPUT section 67 to protect the system against leakage of current and to 
enable cut-off of the power when the computer is not used. Overvoltage 
protection circuit 112 against thunder and a noise filter circuit 111 also 
are included. In view of the fact that high voltage and large current are 
used in the computer, ventilation of the INPUT section 67 is conducted 
through a multiplicity of tiny slits 145 of 4 mm wide and 20 mm long which 
prevents small foreign matters from coming into the INPUT section 67. 
FIGS. 54A, 54B and 54C show the construction of the main AC/DC converter 
70. DC power supply terminals 75a are disposed on the front side, while, 
at the rear side, an aluminum hat dissipation fin unit 62b is attached to 
a heat radiation plate 72a of the main AC/DC converter 70 by means of 
screws. A grease having high heat conductivity is charged between the fin 
unit 62b and the heat radiation plate 72a of the main AC/DC converter 70. 
Both the heat dissipators are made of aluminum. The heat dissipation fin 
unit 62b is 23 mm wide, 85 mm long and 20 mm (4 mm) in fin height, and has 
12 (twelve) fins formed on a fin bade plate of 3 mm thick. Thus, the heat 
dissipation fin unit 62b can be formed by extrusion. The cooling air 2 
flows in the direction parallel to the plane of the base plate of this 
heat dissipation fin unit 62b. 
A light emitting diode is disposed on the front side of the main AC/DC 
converter 70. Lighting up of this light-emitting diode on the front side 
of the main AC/DC converter 70 indicates that breaker 68a of the INPUT 
section 67 is on so that the computer 1000 is being supplied with 
electrical power, thus ensuring safety in the protective maintenance work 
of the computer 1000. A pair of epoxy-type circuit boards are incorporated 
in the main AC/DC converter 70 such that they face each other at their 
surfaces carrying the circuit components. Such circuit components include 
those having large sizes, such as coils 113. 
FIG. 55 shows the construction of an auxiliary AC/DC converter 74. A 
breaker 68b for power storage circuit is disposed on an upper part of the 
front side of the AC/DC converter 74. When this breaker 68b is in the on 
state, the auxiliary AC/DC converter 74 is supplied with electrical power 
even when the breaker 68a of the INPUT section 67 is off, so that the 
auxiliary AC/DC converter 74 is supplied with electrical power, whereby 
the battery 11 is charged through the terminals 75b on the front side. 
Supply of electrical power to the auxiliary AC/DC converter 74 drastically 
decreases when the storage of the battery is completed. The purpose of the 
auxiliary AC/DC converter 74 is to provide a back-up which ensures supply 
of electrical power to the main processing unit 2, I/O package 3 and HDD 
unit 5, in the event of a failure of commercial power or an accidental 
tripping of the power supply. 
The auxiliary AC/DC converter 74 has heat dissipation fin unit 62c on the 
rear side thereof, as in the case of the main AC/DC converter 70. The 
heat-dissipation fin unit 72b is secured to the heat radiation plate 72b 
of the auxiliary AC/DC converter 74 by means of screws. 
The auxiliary AC/DC converter 74 is supplied with electrical power even 
when the breaker 68a of the INPUT section 67 is off. It is therefore 
necessary that an independent cooling means is provided for the auxiliary 
AC/DC converter 74. To this end, an axial fan 23b is mounted on the upper 
part of the rear face of the AC/DC converter 74 and is secured thereto by 
means of screws. An axial fan having an outside dimensions of 
60.times.60.times.25 mm.sup.3, produced by Sanyo Denki Kabushiki Kaisha, 
is used as the axial fan 23b. This fan is driven by a full-speed type 
motor. As shown in FIG. 55, the cooling air forced by this fan flows along 
the heat dissipation fin unit 62c. 
As in the case of the main AC/DC converter 70, the auxiliary AC/DC 
converter has a light-emitting diode 73b which is lit on when power is 
being supplied. This eliminates the danger of electrical shock which 
otherwise may be caused to the user when the user turns to maintenance 
work without knowing that the computer is alive. 
The AC/DC converter 6 is fixed by screws to a metal plate in the casing 1 
by means of screws. In particular, the main AC/DC converter 70 shown in 
FIG. 54 is mounted at a rearward offset of about 50 mm, in order to make 
common use of the upstream portion of the flow of cooling air and the 
mounting fixtures. 
2.7 Main Fan Unit 
FIG. 56 shows the construction of a main fan unit 7a which is disposed 
between the main processing unit 2 and the HDD unit 5 of the computer 1000 
which is an embodiment of the invention and which is shown in FIGS. 7 and 
8. The fan used in this main fan unit 7a is a variable-speed cross-flow 
fan 30 produced by Oriental Motor Kabushiki Kaisha. The rated voltage is 
DC 24V. The dimensions of the fan motor are 76.phi. and 60 mm.sup.3, while 
the dimensions of the impeller are 90.times.90.times.340 mm.sup.3. 
Vibration damping rubber members 77a are provided between the cross-flow 
fan 30 and the bed 76a in support of the fan. As shown in FIG. 35, a duct 
33 is provided in the suction side of the fan. 
As will be seen from FIGS. 58A and 58B, the cross-flow fan 30 includes an 
impeller 30a, a casing 115 which encases the impeller 30a, motor 35 and 
the nose 114. 
According to the described arrangement, it is possible to induce cooling 
air 22 from the bottom region of the main processing unit 2, so that it is 
possible to increase the velocity of cooling air 22 directed to the LSI 
packages 12, IV chips and circuit boards in the CPU package 36, and to 
eliminate any wasteful supply of cooling air 22. 
Furthermore, since the speed of the motor 35 of the cross-flow fan 30 is 
variable, it is possible to avoid supply of excessive cooling air, while 
improving reliability of the bearing and grease of the motor 35. For 
instance, a temperature sensor 34 and a control circuit (not shown) are 
provided on the control circuit board 3c of the basic I/O package unit 3, 
so that the speed of the cooling fan is controlled by the control circuit 
in accordance with the temperature sensed by the temperature sensor 34. 
When the cooling air temperature is 30.degree. C. or below, 17V is 
supplied as the driving voltage, whereas, when the air temperature exceeds 
30.degree., 24V is supplied as the driving voltage, thus causing a change 
in the rate of discharge of air from the cross-flow fan 30. More 
specifically, when the cooling air temperature is high, the difference in 
the temperature between the cooling air and the maximum allowable 
temperature between the unit to be cooled is small, so that the flow 
velocity and, hence, flow rate of the cooling air must be increased in 
order to enhance heat transfer. Conversely, when the cooling air 
temperature is low, the above-mentioned difference in temperature is 
comparatively large, so that the flow velocity and, hence, the flow rate 
of the cooling air can be set low. This control commonly applies also to 
the case of the cross-flow fans 30, 30 of the main fan unit 7b which will 
be mentioned later. 
Vibration damping rubber members 77a exist between the bed 76a and the 
cross-flow fan 30, so that the vibration of the cross-flow fan is never 
transmitted to the computer 1000 and the level of the noise is 
significantly reduced. The duct provided in the air supply portion makes 
it possible to effectively maximize the rate of supply of cooling air to 
the basic DC/DC converter 4a, thus suppressing rise in the temperature. 
FIG. 57 shows a main fan unit 7b which is different from the main fan unit 
7a and which is disposed upstream of the HDD unit 5. This unit 7b has a 
pair of cross-flow fans 30, 30 disposed at an offset from each other. A 
duct 741 (see FIG. 9) constituting a chamber is provided in the discharge 
portion. Vibration damping rubbers 77b are disposed between the bed 76b 
and the cross-flow fan 30. 
The speed of the motor 35 driving the cross-flow fan 30 is variable as in 
the case of the main fan unit 7a, so that wasteful supply of the cooling 
air 22, is avoided while improving reliability of the bearing and grease 
of the motor 35. The vibration damping rubber members 77b between the bed 
76b and the cross-flow fan 30 prevent vibration of the cross-flow fan 30 
from being transmitted to the computer 1000, while reducing the noise. In 
addition, since the pair of cross-flow fans 30, 30 are arranged at an 
offset, it is possible to reduce the interference between these fans, thus 
maximizing the air flow rate and the silencing effect. The duct 741 which 
forms a chamber at the discharge portion ensures that the cooling air is 
uniformly distributed to all HDDs downstream of the fan unit. 
As shown in FIGS. 58A and 58B, the flow velocity of the air at the outlet 
of the cross-flow fan 30 is substantially uniform in the longitudinal 
direction of the impeller 30a but has an offset in the radial direction. 
Such an offset, however, progressively decreases as the air gets farther 
from the fan. The pressure loss of the fan due to flow resistance has a 
certain relation to the velocity. More specifically, in order that the 
pressure loss is reduced, it is preferred that the flow velocity is 
reduced. It is therefore necessary to set the velocity of the cooling air 
to a level which is minimum but high enough to ensure safe cooling of the 
heat source disposed downstream of the fan output. The adjustment of the 
velocity of the air at the fan outlet requires an adjustment of the 
distance between the fan outlet and the heat source. The duct 741 performs 
this function. 
2.8 Back Board 
Back boards are used in this embodiment for the purpose of connecting 
various units. 
2.8.1 Main Processing Unit Back Board 
FIG. 59 illustrates the manner of packaging on the CPU back board 8 of the 
computer 1000 shown in FIGS. 8 and 9. The CPU back board 8 carries 35 
female connectors 48, terminals 75c for supplying power and signals, and a 
grounding terminal 80. According to this arrangement, the main processing 
unit 2, basic I/P package unit 3 and the DC/DC converter 4 are supplied 
with power and signals through the female connectors 48, while supply of 
the electrical power and the signals to the HDD unit 5 and the AC/DC 
converter 6 is conducted via the terminals 75c. This back board is fixed 
to the casing 1 by means of screws. The use of CPU back board 8 is 
advantageous in that it makes it possible to adopt a cable-less structure, 
thus realizing high-density of packaging. 
2.8.2 HDD Back Board 
FIG. 60 illustrates the construction of the storage device unit back board 
(HDD back board) 9 of the computer 1000 shown in FIGS. 8 and 9. The HDD 
back board 9 has 8 female connectors 48 with pins. The leftmost one of 
these connectors is used for supplying electrical power to the DC/DC 
converter. Among the seven remaining female connectors, the first, third, 
fifth and seventh connectors as counted from the right are used for 5-inch 
HDDs, while the first and sixth connectors are used for 3.5-inch HDDs. 
Thus, the HDD back board corresponds to two types of HDDs 108. The pitch 
of the female connectors 48 are substantially constant. This arrangement 
is adopted in order to adapt to a variety of types of HDD 108 and to 
ensure uniform distribution of cooling air 22 to the spaces between 
adjacent HDDs 108 which is offered by the duct 741 which forms a chamber 
an the air supply portion of the HDD. In order that the HDD 108 can be 
inserted and withdrawn in a live state, the HDD back board 9 has a 
structure which provides sufficient strength, i.e., a sufficiently large 
thickness of the package. 
2.9 Circuit Unit 
FIG. 61 shows the construction of a circuit unit 118 of the computer 1000 
shown in FIGS. 8 and 9. There are two types of circuit packages: long type 
circuit package 148 and half-type circuit package 149. This unit further 
has a power supply DC/DC converter 4d. At the front side of the unit, the 
long type circuit package 148 has four male connectors 48, while the 
half-type circuit package has eight male connectors 48. The packages are 
arranged in the direction of flow of the cooling air 22. This arrangement 
permits an efficient cooling, and the unit-type circuits can easily be 
added or removed according to the user's specifications. The unit is 
closed so as not to emit interference electric wave. 
2.10 Cover 
FIG. 62 is a sectional view of the cover 10 of the computer 1000 embodying 
the present invention, in a state in which the cover is attached to the 
top side of the casing. FIG. 62 illustrates the cover 10 which is used 
also as an air supply panel 28. In order to prevent direct emission of 
noise to the exterior through the air supply portion where the cooling air 
22 enters, the portion of the cover 10 in the air supply portion 710 is 
double-walled to have an outer wall 712 and an inner wall 713. A first air 
inlet 714 of the cover 10 for the cooling air 22 is disposed at a right 
position as viewed in the direction facing the cover, while a second air 
inlet 715 formed in the inner wall is deviated in the direction opposite 
to the first inlet 714. The gap between the outer cover and the inner 
cover is reduced without causing reduction in the flow rate of the cooling 
air 22. A filter 29 is provided in the inner inlet for the cooling air 22. 
By maximizing the length of the flow path between the ambient air and the 
interior of the housing, and by reducing the gap between the outer cover 
and the inner cover to minimize the reduction in the cooling air flow 
rate, it is possible to reduce external leak of the noise. Provision of 
the filter in the inner air inlet traps foreign matter so as to prevent 
clogging, thus facilitating maintenance. In this embodiment, a silencing 
material is charged in the inner wall 713. 
2.11 Battery 
FIGS. 63A and 63B are perspective views of the mounted batteries 11 of the 
computer 1000 embodying the present invention. Batteries 11 are used as 
backup members acting in a case where the external power supply is 
interrupted. The batteries 11 are, by a battery cover 61, insulated from 
other structures so as to be free from the flow of cooling air. Four 
batteries 11 are disposed in the battery cover 61, the batteries 11 being 
disposed on the floor of the computer 1000 in consideration of the center 
of gravity of the computer 1000. Since the batteries 11 have considerably 
heavy weight, a handle 146 and rails 147 are provided for the battery 
cover 61 in order to safely and assuredly perform maintenance. When the 
batteries 11 are inserted into the computer 1000, they can automatically 
be introduced into the battery cover 61. 
The structure, operation and effects of this embodiment of the present 
invention will now be described. 
In the foregoing embodiment, the space in the casing has two or more 
systems of flow channels comprising a first flow channel 710 in which the 
main processing unit 2, the basic I/O package unit 3 and the basic DC/DC 
converter 4 are disposed in parallel so that each unit is supplied with 
outer air. As a result, each unit can be cooled with cooling air having 
relatively low temperature. In a second flow channel which is the residual 
flow channel, the HDD unit 5 is disposed at the most upstream position and 
other units are disposed downstream of the HDD unit 5. Thus, the units can 
be supplied with the cooling air in a necessary and sufficient quantity. 
Furthermore, the HDD unit 5 can be supplied with outer air, the 
temperature of which is low and the quantity of which is necessary and 
sufficient. As a result, the HDD 108, which is used in severe temperature 
conditions, can be operated with excellent performance exhibited. 
If a sub-fan unit is individually attached to, for example, the main 
processing unit 2 in case of necessity, the cooling performance can be 
improved. Even if the main supply of cooling air is interrupted, the units 
can be cooled to a minimum degree required. 
A duct 33 is disposed on the air-suction side of the main fan unit 7a so as 
to maintain the quantity of the cooling air. Thus, required cooling of the 
units can be performed regardless of the cross sectional area of the 
opening. As a result, the reliability of the main processing unit and the 
like can be improved. 
By forming the flow channels as described above, the units in the casing 1 
can be cooled to their optimum temperatures without a necessity of 
mounting many fans or using powerful fans. Therefore, this embodiment is 
able to reduce the power of the fans and to decrease the total noise 
generated in the casing. Thus, the cost of the product and power 
consumption can be reduced. 
The main processing unit that considerably generates heat is formed into 
the duct structure and is mounted in a 3D manner so that the cooling air 
can efficiently be used and the size of the casing can be reduced. 
Furthermore, a plurality of hard disk drives are formed into a unit so that 
a great storage capacity is realized. The slide rails disposed in a 
portion of the structure of the unit and on the surface of the casing 
enable the unit to be easily mounted or demounted. The same applies to the 
main processing unit. An employed jig for mounting and demounting 
facilitates the mounting and demounting operation. As a result, the 
working efficiency at the time of performing the maintenance and 
enhancement of the system can be improved. 
In this embodiment, the inlet portion 710 has the panel formed into a 
double-panel structure and the openings shifted mutually so that direct 
radiation of noise generated in the casing is prevented and the lengthened 
radiation channel decreases the noise radiation toward the outside of the 
casing. 
In the exhaust portion 750 employing the punched member having a 
multiplicity of the punched holes, the velocity of the exhaust flow is 
decreased and collision of the exhaust with the floor is moderated so that 
the noise generation is prevented. 
In addition, the weights of the batteries are considered, thus resulting in 
that the batteries are disposed in the bottom of the casing in order to 
make the computer stable. 
Since the resin-molded part is attached to the central recessed portion of 
the front panel in order to prevent distortion in the direction of the 
diagonal lines, the rigidity can be improved even if the weight of the 
front panel is reduced. Since the size of the resin-molded part, that can 
be designed variously, can be reduced and therefore the size of the mold 
can be reduced, a variety of designs can be employed at a low cost. 
As described above, the arrangement of this embodiment is such that the 
number of the fans is decreased to reduce the cooling air discharged from 
the casing. Therefore, noise generation can be prevented, and therefore 
the appearance can be improved, thus resulting in that the office 
environment can be ameliorated. 
In the aforesaid embodiments, the example has been described in which the 
portion in the casing is divided into the two systems of the flow 
channels. However, the present invention is not limited to this. For 
example, the portion may be divided into three or more systems. In a flow 
channel in which units are disposed serially, a bypass channel bypassing 
upstream units may be formed in parallel to the units. As a result, the 
temperature of cooling air to be supplied to the downstream units can be 
lowered. 
As described above, this embodiment produces an effect that each mounted 
unit can adequately be cooled in a forced manner with limited cooling 
units. At this time, noise, hot exhaust air and power consumption can be 
prevented and the cost of the product can be reduced. 
Another embodiment of the air-cooled information processing apparatus 
according to the present invention will now be described. Also the system 
structure according to this embodiment is formed similarly to that 
according to the embodiment shown in FIGS. 1 and 2. Although the exterior 
view of this embodiment is the same as that of the embodiment shown in 
FIGS. 3 to 5, air vents 105 are formed in the side surface of the 
air-supply panel 28 so that access to the computer 1 can be given through 
the front panel 82 which can be opened/closed. 
FIGS. 69 to 71 show a computer 1 according to this embodiment. FIG. 69 is 
an exterior view of the computer 1, FIG. 70 is an exterior view of a 
condition in which the computer 1 is mounted, and FIG. 71 is a partial 
sectional view of the computer. This embodiment has an arrangement that 
the resin-molded portion 86 to be received in the recessed portion 85 of 
the front panel 82 is divided into a plurality of small panels 87 to 92 
and that the recessed portion 85 corresponding to the small panels 87 to 
92 has an opening so that a function portion is added to the resin-molded 
portion 86. 
Referring to FIG. 69, reference numeral 1 collectively represents a main 
body of the computer 1 including a control processing apparatus, the main 
body being formed into an elongated box-like shape in the longitudinal 
direction. The computer 1 is composed of a front panel 82 forming the 
front surface of the computer 1 and made of a steel plate, a main box 83 
forming the rear portion of the computer 1 and a base portion 84 forming 
the bottom portion of the computer 1. 
The front panel 82 has a flat portion in the form of a gate-like shape 
connected to the two sides in the lengthwise direction and to the upper 
portion, a recessed portion 85 (shown in FIGS. 70 and 71) formed in this 
way that the flat portion is left, and a resin-molded portion 86 received 
in the recessed portion 85. The resin-molded portion 86 is formed by small 
panels 87 to 92 stacked vertically and has two longitudinal ends that 
coincide with the front panel 82, the resin-molded portion 86 being formed 
by a curved surface having a projecting central portion. In this 
embodiment, the small panels 88 to 91 are formed into 
magnetically-shielded bezels (a front panel 82) for various 
recording/reproducing apparatuses. The detailed description of the bezels 
will be made later. 
The main box 83 is composed of a ceiling plate 94, two side plates 95 and a 
back plate 96 attached to a frame 93 (shown in FIG. 71) of the computer 1. 
Although omitted from the illustration in this embodiment, portions for 
establishing connections with various units and heat-radiating portions 
are concentrically disposed on the back plate 96. 
The base portion 84 has a skirt portion 26 made of plain portions and 
formed in the periphery thereof, the skirt portion 26 having casters (not 
shown) therein to hide the casters from outside. The base portion 84 is so 
disposed as to accommodate units to be disposed on the base portion 84 
within an area to which the base portion 84 is projected so that the base 
portion 84 serves as a bumper acting when the computer 1 is moved. 
In FIGS. 70 and 71, the end of the periphery of the front panel 82 has a 
bent frame 97 formed by bending the front panel 82. At an end of the bent 
frame 97, a U-shape mounting portion 98 is formed. Each of the two side 
plates 95 of the computer 1 is bent to be formed into an L-shape at the 
end thereof so that the two side plates 95 reach the frame 83 of the 
computer 1. The front panel 82 is attached such that the bent frame 97 in 
the upper portion of the front panel 82 is hooked on a frame 93 (not 
shown) of the computer 1 so that the mounting portion 98 abuts against the 
L-shape portion of the two side plates 95. The lower portion of the front 
panel 82 is secured to the frame 93 with screws 78. 
As described above, the resin-molded portion 86 is composed of the plural 
small panels 87 to 92 which are stacked up, the small panels 87 to 92 
being received in the recessed portion 85 of the front panel 82 and 
attached from inside by attaching means, such as screws, so that the upper 
and lower members continue to each other. 
In this embodiment, the uppermost small panel 87 is formed into a sash 
portion serving to locate the top end of the resin-molded portion 86 and 
to improve the appearance. The lowermost small panel 92 is formed into a 
decoration panel having a pattern 99 having projections and recesses. The 
small panel 88 disposed between the small panel 87 and the small panel 92 
is formed into a bezel forming the front panel 82 of the DAT device 31. 
The small panel 89 is formed into a bezel for the magnetic tape cassette 
unit, the small panel 90 is formed into a bezel for the compact disk 
device, and the small panel 91 is formed into a bezel for the 8 mm 
magnetic tape device. The recessed portion 85 in the front panel 82 
corresponding to the small panels 88 to 91 has an opening portion 100 into 
which the body of the recording/reproducing apparatus (the body 31a of the 
DAT device 31) is inserted. The opening portion 100 is so formed as to 
leave a flat portion formed into a square-frame shape in the recessed 
portion 85 in the periphery of the opening portion 100. Thus, the 
recording/reproducing apparatus (the DAT device 31) is mounted in this way 
that the flat portion in the form of the square-frame shape is surrounded 
by the bezels 88 to 91 by means of a rein-forming member 101. The small 
bezel 92 employs, on the outer surface thereof, the projecting curved 
surface which has the pattern 99 having projections and recesses thereon 
so that its rigidity is improved to serve as a bumper. Since the structure 
is arranged such that the screw 78 for securing the front panel 82 is 
inserted into a through hole 102 formed in the pattern 99 having the 
projections and recesses and formed in the small panel 92, adverse 
influence upon the design due to the appearance of the screw 78 can be 
prevented. 
In this embodiment, the exterior color of the computer 1 is made achromatic 
mainly composed of gray to be matched to the environment of the computer 
1. Furthermore, color of coating the front panel 82 and the main frame 83 
is different in the color tone from that of the resin-molded portion 86 
disposed adjacently to the front panel 82. Therefore, the computer 1 
matches the achromatic color employed in many office floors from a 
distance so that the computer 1 harmonizes with the floor of the office. 
The difference in the color tone employed in this embodiment eliminates a 
necessity of considering color mismatch occurring due to the difference in 
the materials taking place in a case where the steel plate and the resin 
are disposed adjacently and that due to the difference in the aging speed 
of the materials. 
As described above, this embodiment enables the overall body of the 
computer 1 to be covered with the steel plate so that the magnetic shield 
effect is produced. Since the resin-molded portion 86 is received in the 
recessed portion 85 formed in the central portion of the front panel 82, 
the distortion in the diagonal direction of the front panel 82 can be 
prevented, thus resulting in that the front panel 82 can be lightened and 
its rigidity can be enhanced. Since the size of the resin-molded part 86, 
that can be designed variously, can be reduced and therefore the size of 
its mold can be reduced, a variety of designs can be employed at a low 
cost. 
Since the resin-molded part 86 is made to project, the resin-molded part 86 
is able to have the bumper function. Furthermore, the pattern 99 having 
projections and recesses and formed in the resin-molded portion 86 further 
strengthens the resin-molded portion 86 and the front panel 82. 
Since the resin-molded portion 86 is formed by the plural small panels 87 
to 97 disposed in line in the lengthwise direction, the size of the 
resin-molded part 86 can further be reduced. Since the small panels 88 to 
91 are formed into the bezels for the storage units, minor changes of the 
small panels 88 to 91 enable a series of products having a variety of 
functions to be realized. 
Although this embodiment has the arrangement that the small panels 88 to 91 
are formed into the bezels, some small panels may be formed into simple 
decoration covers if necessary for the employed arrangement of the series 
of the models of the computers. In this case, steel plates are attached on 
the inside of the decoration panels so that the computer 1 is magnetically 
shielded. 
The arrangement of the mounted structure is made as shown in FIGS. 72 to 
74. 
An embodiment shown in FIG. 72 has an arrangement that two systems of flow 
channels are formed, the overall body of the casing is cooled by two 
once-through fan 13, and a slitted duct 8 is formed upstream of the upper 
once-through fan 13. As a result of the thus-made structure, the circuit 
board 1, the OSC board 2 and another circuit board 1 and devices mounted 
on the electronic equipment can satisfactorily be cooled. 
In this embodiment, the CPU portion generating great heat is cooled by the 
duct 8 having an axial fan 23a. Namely, the flows of the air in front of 
and in the rear of the fan are controlled to cool the heat-generating 
portions (the heat spots) with minimum air quantity, resulting in that the 
overall body of the casing can be cooled even if the performance of the 
fan is limited. The OSC board 2 adjacent to the CPU portion is cooled in 
this way that its one side is cooled by jet stream from the axial fan 23a 
and the residual side is cooled by parallel flows created by the 
once-through fan 13. As compared with a case where the two sides are 
cooled by parallel flows created by the once-through fan 13, the devices 
on the circuit board 1 can be cooled satisfactorily. Since also the OSC 
board 2 is cooled on the two sides thereof by the jet streams, sufficient 
cooling performance can be obtained. Although the duct 8 is, in this 
embodiment, connected to the casing 12, the duct 8 may be formed into a 
detachable structure. In this case, conversion to a structure 
corresponding to the heating value of the memory 4 and the like can be 
realized to enhance the cooling effect. Moreover, there can be made 
structure to cope with trend of generating larger heat values involved in 
the version-up of the model of the computer. 
The size of the foregoing electronic unit 12 is 300 mm wide, 700 mm high 
and 800 mm deep. 
Although the mounted structure is made to be similar to that of the 
embodiment shown in FIGS. 8 to 10, a locally-cooling fun unit 7c has: an 
axial fun 23a: (80.times.80.times.25)m.sup.3 manufactured by Sanyo 
Electric; and a jetting-out port 24 which is a port through which cooling 
air 22 jets out. There are disposed casters 25 and a skirt 26 in the 
bottom portion of the computer 1. The punched member 27 having the punched 
holes having a diameter of 2 mm and 4 mm is disposed in the air-exhaust 
portion of the computer 1. An air-supply panel is attached on the rear 
side serving as the air intake portion for the computer 1, the air-supply 
panel also serving as a cable cover 10. The air-supply panel includes a 
filter for preventing suction of dust or the like, the filter being 
attached to the air vents 105 with a magic tape. 
Although the structure for local cooling is arranged similarly to that of 
the embodiment shown in FIGS. 11 to 12, the CPU portion 2 has, therein, a 
multiplicity of guide rails 44 for facilitating insertions of the RISC 
processor module 15, the OSC package 16 and the MS middle card 19 into the 
main CPU package 36. Incidentally, even if the rotations of the cross-flow 
fan 30 for cooling the overall body of the computer 1 are stopped, cooling 
of the RISC-T package 15 can be performed continuously so far as the axial 
fan 23a is operated. 
As shown in FIGS. 72 to 74, the computer 1 includes the two flow channels 
through which the cooling air 22 flows. FIG. 75 is a cross sectional view 
taken along line LXXV--LXXV of FIG. 72. Referring to FIG. 75, the cooling 
air 22 in the first flow channel is introduced through the air-supply 
panel 28 disposed on the rear side of the computer 1, allowed to 
horizontally pass through the CPU portion 2, sucked through the bottom 
portion of the CPU portion 2 by the cooling fan unit 7a comprising the 
cross-flow fan 30, and discharged from the cross-flow fan 30 having an 
angle of 45.degree. so that the direction of the cooling air 22 is 
perpendicularly bent downwards. Then, the cooling air 22 is allowed to 
pass through the portions of the DAT 31, the HDD unit portion 5 and the 
AC/DC converter portion 6, and then it is discharged through the punched 
member 27 on the floor plate. Then, the cooling air 22 is allowed to pass 
through a portion below the skirt 26 and discharged to the outside portion 
the computer 1. In particular, the locally-cooling fan unit composed of 
the axial fan and the rectangular jetting-out port is disposed upstream of 
the RISC processor module in the CPU portion 2 on which the RISC chip 
package generating great heat and the cache memory (for details, see FIG. 
12) for temporarily storing data are mounted. The hard disk drives in the 
HDD unit portion 5 are disposed at different intervals in order to improve 
the cooling efficiency. As for this arrangement, it will be described 
later with reference to FIG. 79. 
The second flow channel for the cooling air 22 is so arranged that the 
cooling air 22 is introduced through the air-supply panel 28 serving as an 
air vent, that is the same as that for the first flow channel, allowed to 
horizontally pass through the I/O package portion 3, allowed to downwards 
pass through the duct 33 formed by insulating walls 32 of the first flow 
channel and the second flow channel, and then sucked by the cooling fan 
unit 7b comprising a cross-flow fan 30 on a market. After the cooling air 
22 is discharged from the cross-flow fan 30 having an angle of 20.degree., 
it is bent, allowed to pass through the DC/DC converter portion 4, 
discharged through the punched member 27 of the floor plate similarly to 
that in the first flow channel, allowed to pass through a portion below 
the skirt 26 and discharged to the outside portion of the computer 1. 
Since the cross-flow fan 30 is mounted while being angled by 20.degree., 
the cross-flow fan which is a mass-produced product on the market can be 
employed, thus resulting in that the cost to manufacture the computer 1 
can be reduced. 
The cross-flow fan 30 has a signal line to receive a signal from the 
temperature sensor attached to a control circuit board of the I/O package 
portion 3 disposed adjacent to the inlet portion so that the speed of the 
revolutions of the motor is varied in response to the signal supplied from 
the temperature sensor in order to improve the cooling efficiency. The 
foregoing effect can be realized by preparing a table of the temperatures 
and the speed of the revolutions and by supplying a signal for controlling 
the speed of the revolution in accordance with the table from the I/O 
package portion 3 to the cross-flow fan 30. 
The provision of the two systems of the cooling flow channels in the 
computer 1 prevents the rise in the temperature of the air in each flow 
channel, lowers the temperature level at each heating generating member, 
and makes uniform the temperature distribution among the heating 
generating members as compared with a case in which a single flow channel 
is provided. Further, the cooling fan disposed upstream of the heat 
generating members enables high-speed cooling air to be supplied to the 
heat-generating units, raising the heat transfer from the cooling air and 
thus lowering the temperature of the heat generating members. 
Further, the cooling flow channel is so formed into the two systems as to 
make the required flow quantity to be the same for the two flow channels. 
The aforesaid arrangement can be realized by determining the configuration 
of the modules in consideration of the capacity of each flow channel and 
the average value of the heating values of the heat generating members. 
The reason why the heating value of each flow channel and the required 
quantity of the cooling air are uniformly distributed is that the loads on 
the fans must be equally divided to prevent offset of the quantity of 
noise generated in the air flow channels. If the flow quantity of either 
of the cooling air flow channels is set to a large quantity resulting in 
that the offset of the noise takes place, noise insulation by means of the 
casing becomes a necessity of taking vibration and noise preventive 
countermeasures capable of preventing the noise generated in either of the 
cooling air channels that generates noise of higher level, that is, a 
countermeasure of thickening the wall of the casing. Thus, wasteful 
countermeasure must be taken. This embodiment employs the two systems of 
the flow channels in consideration of the quantity of the cooling air 
required for each portion so that a design for silent structure is 
realized. 
The method of cooling the computer 1 according to this embodiment has the 
arrangement that the cross-flow fan 30, which is the noise source, is 
disposed apart from the air vents 105 and the exhaust holes 119 so that an 
effect of preventing noise leakage is produced. With the foregoing cooling 
structure, it is effective to dispose the cross-flow fan 30 which is 
suitable to widely and uniformly form air flows. Since the cross-flow fan 
30 generally employs accelerating wing cascade, a high flow velocity is 
obtained at the outlet port of the fan. Therefore, the cooling structure 
is employed in which the HDD unit portion 5 and the DC/DC converter 
portion 4, which are heat sources of a type generating a great heat 
quantity and which are effective to be supplied with the high-speed 
cooling air 22, are disposed adjacently to the outlet port of the 
cross-flow fan 30. As a result, the structure of the casing is achieved 
which is capable of realizing efficient cooling and preventing generation 
of noise. 
Since the hard disk drives are disposed at different intervals, the 
distribution of the cooling air to the AC/DC converters 6 downstream of 
the HDD units can be made to be sufficient to cope with the heating value 
of each of the AC/DC converters 6. Therefore, the temperature of the AC/DC 
converters 6 can be made to be uniform. 
Since the cross-flow fan 30 is disposed in the computer 1, there can be 
prevented leakage, to the outside of the computer 1, of noise generated 
due to the rotations of the cross-flow fan 30 and collision noise 
generated due to collision with the substance at the outlet port of the 
cross-flow fan 30, thus resulting in a satisfactory effect of eliminating 
noise. The disposition of the skirt 26 in the bottom portion of the 
computer 1 significantly prevents noise generated when the cooling air 22 
collides with the floor and prevents flying of dust and the like in the 
room in which the computer 1 is installed. 
Further, the exhaust port for the cooling air is disposed in the lower 
portion of the computer 1 so as to be disposed apart from the cross-flow 
fan 30. In the portion below the HDD unit 5 and the like which are the 
heat sources, the punched member 27, the diameter of which is 2 mm or 
less, is used to form the surface of the portion below the heat source in 
order to prevent start of a fire due to accidental fall of sparks from the 
heat source onto the floor. The disposition of the punched member 27 
having the diameter of 2 mm and 4 mm to form the exhaust surface of the UL 
standard enables the flow velocity in the exhaust portion to be decreased 
and noise and the like generated when the cooling air 22 collides with the 
floor to be significantly eliminated. If the exhaust port for the cooling 
air 22 is disposed below the heat source, the flow of the cooling air 22 
must be exhausted to the outside portion of the computer 1 through the 
punched member 22 having the diameter of about 2 mm or less. If the 
cooling air 22 is exhausted through such small holes, the pressure loss is 
enlarged and the static pressure of the fan must be raised. Thus, the load 
for the cooling fan is made to be heavy and a tendency arises in that the 
noise is enlarged. In order to overcome the problems, another embodiment 
of section LXXV--LXXV of FIG. 72 is shown in FIG. 76. As shown in FIG. 76, 
a bent duct 103 is attached to a portion below the heat source to prevent 
the fall of sparks from the position immediately below the heat source. An 
exhaust port formed in the leading portion of the bent duct 103 prevents 
the pressure loss in the flow channel. The bent duct 103 in the exhaust 
portion collects the cooling air 22 into the central portion of the lower 
portion of the computer 1 and then exhausts the same to the outside 
portion of the computer 1. Since the effect of eliminating the noise is in 
proportion to the distance for which the noise is transmitted from the 
inside portion of the computer 1 to the outside portion of the same, the 
disposition of the bent duct 103 produces an effect of eliminating the 
noise. 
The capability of varying the speed of the revolutions of a motor 35 
through the signal line of the motor 35 for the cross-flow fan 30 
connected to the temperature sensor 24 attached to the control circuit 
board in the I/O package portion 3 adjacent to the inlet portion enables 
the life of the motor to be lengthened, the power consumption for the 
motor 35 to be reduced and also the power consumption of the computer 1 to 
be reduced. In addition, another effect can be produced to eliminate the 
noise in the computer 1. 
The foregoing effect is obtained from a structure in which the control 
circuit board is disposed in, for example, the I/O package portion 3, the 
control circuit board controlling the speed of the revolutions of the 
motor 35 for the cross-flow fan 30. If the temperature of the supplied air 
is 30 degrees or lower, the drive voltage is set to 17V. If it is 30 
degree or higher, the drive voltage is set to 24V. Thus, the quantity of 
the supplied cooling air 22 from the cross-flow fan 30 can be varied. That 
is, if the temperature of the supplied air is high, the difference between 
the allowable temperature for the semiconductor and the like mounted on 
the circuit board and the temperature of the air is decreased, resulting 
in a necessity to arise in the quantity of the cooling air 22 and the 
velocity of the same is raised in order to enhance the heat transfer with 
air. If the temperature of the cooling air 22 is low, the foregoing 
difference in the temperature is permitted to be enlarged. Therefore, the 
quantity of the cooling air 22 can be enlarged and the velocity of the 
same can be decreased. Since the speed of the revolutions of the motor 35 
for the cross-flow fan 30 can be varied to a low speed, another effect of 
eliminating the noise of the computer 1 can be obtained. Furthermore, the 
provision of the air-supply panel 28 and mounting of the filter on the 
inlet portion prevent the leakage of the noise toward the outside portion 
of the computer 1, thus resulting in an effect of noise elimination. 
Another embodiment is shown in FIGS. 92 to 94. This embodiment provides an 
extension casing for the computer 1 according to the foregoing 
embodiments. Similarly to the foregoing embodiments, two systems of 
cooling flow channels are formed. One of the flow channels is so formed 
that cooling air is introduced through the air-supply panel 28, allowed to 
pass through the cross-flow fan 30 on the market and a line unit 118 and 
then discharged outside through the bottom portion of the computer 1. As 
shown in FIG. 95, the line unit 118 is mounted in the same direction as 
the direction in which the cooling air 22 flows at the outlet port of the 
cross-flow fan 30 in order not to go against the flow of the cooling air 
22. Another flow channel is so arranged that cooling air is, similarly to 
the first flow channel, sucked through the air-supply panel 28, allowed to 
pass through the DC/DC converter 4, discharged from the cross-flow fan 30, 
allowed to pass through the HDD unit portion 5 and the AC/DC converter 
portion 6 similarly to the first embodiment, and then discharged outside 
through the floor of the computer 1. In this case, the cross-flow fan 30 
is mounted while being inclined similarly to the foregoing embodiments. 
FIG. 96 is a detailed view of the DC/DC converter portion 4 and the 
cross-flow fan 30 in the second flow channel. In order to make cooling air 
flow through the circuit board for the DC/DC converter 4, the DC/DC 
converter portion 4 is disposed in parallel to the direction in which the 
cooling air flows. In order to efficiently use the cooling air 22, the 
cross-flow fan 30 is angled so as to suck the cooling air 22 from portions 
except the DC/DC converter portion 4. As a result, the air quantity 
obtainable from the cross-flow fan 30 can be used most efficiently. 
Furthermore, the package 36 forms a portion of the duct. 
Incidentally, the CPU unit portion has the structure shown in FIGS. 37 and 
38. 
The packaging structure of the main CPU package 36, packaging structure of 
the RISC processor module 15 and the packaging structure of the MS package 
18 and the MS middle card 19 are as shown in FIGS. 41, 11 and 42, 
respectively. 
FIG. 77 shows the manner of packaging of the BA package 20. The BA package 
has a pair of LSI chips 53 and four male connectors 49d. Three of these 
male connectors 49d are for mounting on the main CPU package 36, while the 
remaining one is used for external control. The role of the BA package 20 
is to act as a relay between different signal lines. In order to transfer 
high speed signals to other packages without reducing the signal rate, the 
central male connector 49d among the above-mentioned three male connectors 
49d functions as an input terminal, while the pair of male connectors 49d 
on both sides serve as output terminals. The entered signals are shared to 
the above-mentioned two LSI tips 53. The LSI chips 53 are mounted in 
180.degree. reverse to each other so as not to retard the signal 
transmission. The mounting and demounting of the BA package 20 is 
conducted by means of a hand lever 54 (see FIG. 48) having projections 47c 
engageable with small holes 46i formed in the BA package 20. 
The RISC processor modules 15, OSC package 16, MS middle card 19 and the BA 
package 20 are mounted on the main CPU package 36 in the manner shown in 
FIG. 37. The handle lever 54 used as a separate jig has a construction as 
shown in FIG. 44. The slide rails 40 and the CPU unit are mounted in the 
computer in the manners shown in FIGS. 45A, 45B, 37 and 38. 
The mating connectors, male and female, are constructed such that a 
multiplicity of electrical signal pins provided in the female connector 
48e are received in corresponding holes formed in the male connector 49e, 
thus achieving the electrical connection. 
The CPU unit 2 has a duct-like construction and all the packages in this 
unit are arranged in the same direction so as to allow the cooling air to 
easily flow through this duct. Part of this duct is constituted by the 
main CPU package 36. The air supply and discharge portions of this duct 
have guide rails 44 and metal plates which are used for supporting the 
aforementioned packages. The portion of the duct upstream of each package 
has a rectangular opening 58a shaped and sized so as to correspond to the 
package. Through these openings 58a, cooling air 22 is supplied to the 
respective packages at flow rates corresponding to the rates of generation 
of heat from the respective packages. In addition, restriction of the 
supply or inlet portion of the duct eliminates the supply of wasteful 
cooling air 22, while enhancing the flow velocity of the cooling air. At 
the same time, temperatures of the semiconductor elements in the 
respective packages are cooled down to improve the reliability and 
computing performance. 
The construction of the I/O package is the same as that shown in FIG. 46. 
Each package carries a multiplicity of semiconductor chips. A battery cover 
61 is so mounted that the cooling air 22 is supplied from one lateral side 
of each package and then flows through the package. 
FIG. 72 shows a computer as an embodiment of the present invention. This 
computer 1 has a DC/DC converter unit 4 having four stages or layers. 
These stages are the first and second stages from the top, having 
constructions as shown in FIG. 47, and third and fourth stages having 
constructions as shown in FIG. 48. The first stage is capable of supplying 
5V.times.36 A power and 3.3V.times.3 A power, the second stage is capable 
of supplying 5V.times.17 A power and 12V.times.11 A power, the third stage 
is capable of supplying -12V.times.3 A power and the fourth stage is 
capable of supplying auxiliary power supply 12V.times.2 A and 5V.times.7 A 
power. The conversion efficiency of the DC/DC converter 4 is 78%. The heat 
dissipation rates of the first, second, third and fourth stages are 
respectively 53 W, 59 W, 9 W and 14 W. 
The velocity of the cooling air discharged from the cross-flow fan 30 is 
high. A commercially available cross-flow fan made of Oriental is suitably 
used as the cross-flow fan. Since this cross-flow fan is installed at an 
inclination angle of 20.degree., the first and the second stages of the 
DC/DC converter, which are circuit boards generating heat at large rates, 
are supplied with the cooling air 22 of high velocity. 
The HDD unit has a construction as shown in FIGS. 51 and 71, and the top 
plan view of the HDD unit 5 of the computer of FIG. 72 is shown in FIG. 
79. It will be seen that the spacing between adjacent HDDs 108 is large in 
the central region of the HDD unit 5. This large space is intended to 
supply cooling air 22 at a sufficiently large rate to the main AC/AC 
converter 70 which is at the center of the AC/DC converter 6 located 
downstream of the HDD unit 5. This contributes to improvement in the 
reliability of the AC/DC converter 6. 
FIG. 80 shows the construction of the INPUT section 67. The INPUT section 
67 is located at right side as viewed in the direction normal to FIG. 11 
and is supplied with A.C. 100V through a power supply cable connector 66. 
A breaker 68a is mounted in upper part of the INPUT unit 67 to provide 
protection against leakage of current and to provide means for cutting off 
the power when the computer is not used. A pair of service receptacles 69 
are provided to enable supply of power when the system it to be expanded. 
The receptacles 69 become operative only when the computer 1 is operating. 
Anti-thunder overvoltage protection circuit 112 and a noise filter circuit 
111 also are incorporated. 
The construction of the main AC/DC converter unit 70 has a construction as 
shown in FIG. 54. The AC/DC converter 70 is located at a central portion 
as viewed in the Figure. The specifications of this converter are 52V, 11 
A and 580 W. The power factor is 85%. 
FIG. 81 shows the construction of the auxiliary AC/DC converter 74. The 
auxiliary AC/DC converter 74 is disposed at the left side as viewed in 
FIG. 72. Other portions are materially the same as those shown in FIG. 55. 
The cooling fan unit has a construction as shown in FIG. 82. This 
construction is substantially the same as that shown in FIG. 56. 
When the temperature of the cooling air is low, the difference between the 
air temperature and the maximum allowable temperature is comparatively 
large, so that the flow velocity and, hence, the flow rate of the cooling 
air can be set low. In addition, vibration damping rubber members 77a 
between the support plate 76 and the cross-flow fan 30 prevent the 
vibration of the cross-flow fan 30 from being transmitted to the computer 
1, thus contributing to reduction in the noise level. 
FIG. 83 shows another arrangement in which a fan different from the fan 7a 
is disposed upstream of the DC/DC converter 4. In order to uniformalize 
the velocity of the air passing through the I/O package 3, ducts are 
formed at the outlet side of the I/O package 3 and the suction side of a 
cross-flow fan 30. As staged before, the first, second, third and fourth 
layers or stages of the DC/DC converter 4 have electrical power capacities 
of 190 W, 220 W, 40 W and 60 W, and generate heat at rates corresponding 
to the power capacities. Thus, the first, second, third and fourth stages 
produce heat at rate of 53 W, 59 W, 9 W and 14 W. In order to develop 
uniform temperature distribution over the LSI packages 12, IC chips and 
other elements on the circuit board of the DC/DC converter 4, it is 
necessary to suitably determine the velocities and flow rates of the air 
to be supplied to respective stages of the DC/DC converter 4 in accordance 
with the rates of heat generation. More particularly, it is necessary that 
the cooling air 22 is supplied at specifically large rates to the first 
and second stages of the DC/DC converter 4 which produce heat a large 
rates. To realize such cooling conditions, a commercially available 
cross-flow fan 30 is used in such a posture that the fan 30 has been 
rotated through 20.degree. in the same horizontal direction. To this end, 
a support plate 76b is attached to the cross-flow fan 30. A vibration 
damping rubber 77b is interposed between the support plate 76b and the 
cross-flow fan 30. The motor 35 driving the cross-flow fan 30 is 
speed-variable as in the case of the aforesaid fan 7a, so that it is 
possible to eliminate wasteful supply of the cooling air 22 while 
improving reliability of the bearing and the grease. For instance, the 
speed of the cross-flow fan 30 is controlled by a control circuit board 
provided in the I/O package 3. For instance, when the temperature of the 
cooling air is 30.degree. C. or less, 17V is supplied as the driving 
voltage, whereas, when the air temperature exceeds 30.degree. C., 24V is 
supplied as the driving voltage, whereby the rate of discharge of the 
cooling air from the cross-flow fan 30 is varied. More specifically, when 
the temperature of the cooling air is high, the difference between the 
cooling air temperature and the maximum allowable temperature of the 
semiconductor devices or the like to be cooled in the circuit board is 
correspondingly small, so that the air flow velocity and rate have to be 
increased in order to promote heat transfer between the air and the 
semiconductor device. In contrast, when the cooling air temperature is 
low, the above-mentioned temperature difference is comparatively large, so 
that the flow rate and velocity of the cooling air 22 may be set low. 
FIGS. 84, 85 and 86 show the manner in which the fan is mounted. An 
experiment showed that the arrangements shown in FIGS. 84 and 85 do not 
provide high cooling efficiency because cooling air of high velocity 
impinges upon the wall of the casing or the HDD unit 5. FIG. 86 shows an 
improved arrangement which employs a cross-flow fan. This cross-flow fan 
has a casing 115 defining fan inlet and outlet, the fan outlet being bent 
at an angle greater then a right angle relative to the fan inlet. This 
type of fan exhibits such a pattern of flow velocity distribution of the 
discharged air that the flow component adjacent to the casing, which 
exhibits the highest velocity, is directed to a region spaced away from 
the heat source, whereas the flow component adjacent to the fan nose 114, 
which has slow velocity and encounters reduced resistance, approaches the 
heat source. Consequently, the high-velocity flow component adjacent the 
casing merges into the low-velocity flow component adjacent to the nose, 
whereby the overall resistance is reduced while the required flow velocity 
is obtained. There are only few fans having this type of casing in 
commercial market. Using different fans of different configurations 
corresponding to various cooling requirements of different units to be 
cooled is useless and increases the number of parts to raise the cost. In 
the embodiment shown in FIG. 87, therefore, a commercially available 
through-flow fan, having an outlet bent at about a right angle with 
respect to the inlet, is installed in the casing at a suitable 
inclination. This arrangement provides an effect substantially equivalent 
to that obtained when the configuration of the casing of a cross-flow fan 
is varied. Thus, the embodiment shown in FIG. 87 makes it possible to 
obtain a cooling system capable of producing high cooling effect and 
operable at reduced noise level, without using any specially designed 
fans. 
FIG. 88 shows an embodiment which employs a cross-flow fan installed in the 
cooling air channel. In this case, the distance is smaller at the casing 
side 115 than at the nose side 114. In this case, however, the pressure 
drop is lower than that produced when the fan is installed such that the 
fan casing outlet is disposed in parallel with the circuit board. 
In the two examples described above, the cooling performance is improved by 
increasing the distance between the fan outlet and the heat source. Such 
an increase in the distance may be realized by obliquely installing the 
fan or by translationally moving one of the fan and the heat source 
relative to each other. It is to be understood that the former method, 
i.e., oblique installation of the fan, provides a greater space factor 
inside the casing than the latter method. 
FIG. 89 is a bottom plan view of the computer 72 shown in FIG. 72 embodying 
the invention. In order to improve the space factor of the casing, the 
width of the casing is set substantially equal to the circuit board. In 
order to realize efficient cooling under this condition, heat dissipation 
fin unit 62b for power supply is disposed at a position opposite to the 
motor 35 where the cooling air encounters smaller resistance, so that the 
air can be concentrated to the region around the fan, thus enhancing the 
cooling effect. 
FIG. 90 shows the construction of a HDD back board unit 9 of a computer 1 
shown in FIG. 72. There are eight female connectors 48 having pins in the 
HDD back board unit 9. The spacing between adjacent female connectors 48 
is greater in the central region of the HDD back board unit 9. 
Consequently, when the HDD is mounted on the computer 1, the size of the 
gap between adjacent HDDs, which form passages for the air, is greater in 
the central region than in the peripheral region. With this arrangement, 
it is possible to supply cooling air at a specifically large rate to the 
main AC/DC converter 70 which is a heat source generating heat at 
specifically high rate and which is positioned in the center of the AC/DC 
converter 6 installed downstream of the HDD unit 5, thus meeting the 
requirement for enhancement of cooling effect on the main AC/DC converter 
70. 
FIG. 91 shows the construction of a cable cover unit 10 of a computer 1 
which is a different embodiment of the invention. More specifically, this 
Figure shows a silencing structure making use of the cable cover unit 10. 
In order to prevent the noise from directly propagating to the exterior 
through the suction of the cooling air fan, a chamber 116 is defined on 
the back side of the computer 1 by a cable protection cover 10. An intake 
opening 117 formed in the cover 10 is deviated from the suction opening 
105 so that the suction opening is not directly exposed to the exterior, 
thus achieving noise confining effect. 
The embodiments of the invention described hereinbefore offers the 
following advantages. 
At least two cooling air flow channels are formed in the casing. In 
addition, various measures are taken such as installation of a cooling air 
fan between adjacent heat-generating units to be cooled, downward 
orientation of the cooling air discharge passage, spacing cooling air fans 
apart from each other and/or provision of double-walled portion in the 
casing. Consequently, temperature rise of the cooling air inside the 
casing is suppressed and uniform temperature distribution is developed 
over heat-generating units in the casing. In addition, the fan driving 
power is reduced, as well as the level of the noise. 
By obliquely installing a cross-flow fan at a bend of each of two or more 
cooling air flow channels, it is possible to improve the space factor and, 
hence, to miniaturize the casing. 
By constructing a CPU package as high-rate heat generator in a duct-like 
configuration, and by adopting three-dimensional mounting, it is possible 
to make an efficient use of the cooling air to enable reduction in the 
size of the casing. 
In a specific form of the invention in which a duct is provided on the 
suction side of a cross-flow fan, it is possible to make an efficient use 
of the cooling air and to enhance the performance of the fan. 
In another specific form of the invention, a resin mold part is fitted in 
the central recess of a front panel of the casing, thus stiffening the 
front panel against distortion about diagonal lines, while reducing the 
weight of the front panel and enhancing the rigidity of the same. 
The resin mold part, which can have a variety of designs and which can be 
formed small in size, makes it possible to obtain front panels having 
different designs.