Parallel system bus structure

Abstract: Disclosed is an improved parallel system bus structure comprising a plurality of bus wire-printed disks (5) each having a plurality of signal conductors (6) of equal length extending radially from a common central contact (7). These bus disks (5) are spaced vertically at regular intervals, and a plurality of connectors (12) are fixed to the circumference of the bus disks to permit connection between the signal conductors of the bus disks and the terminals of the CPU board. The radial arrangement of signal conductors (6) permits connection of selected CPU boards via equal length signal paths, no matter how many CPU boards may be used.

Description: The present invention relates to an exterior bus for a microprocessor computer. A conventional hardwear structure of a multi-microcomputer system uses a plurality of CPU boards each having a central processing unit built thereon, and these CPU boards are mounted in a frame with their main surfaces parallel with each other. The lead conductors which are terminated at the inside edge of each CPU board, are connected to a bus cable extending behind the frame via an appropriate connector. In the conventional multi-microcomputer system a plurality of CPU boards are arranged with their main surfaces parallel with each other to form a single line, and these CPU boards are connected to a single bus cable. As a consequence the distance between two CPU boards selected among a series of boards may depend on which positions such CPU boards are put, varying greatly with the increase of the number of the series-connected boards. In case of communication between selected CPU boards via the bus cable, the signal path whose length is dependent on which boards are selected, must be taken into consideration for well-timed operation. As shown in Figure 13, a plurality of air conditioning fans 21 are arranged along the line of CPU boards 20. CPU boards which are positioned near each fan will be cooled more than those which are positioned far from each fan, and therefore, it is difficult that all CPU boards are cooled evenly and kept at same temperature. An alternative conventional bus structure is described in US-A-4679872. A cylindrical back plane structure includes a plurality of conductive spiders, each having a plurality of conductive legs, each of which makes electrical contact with an edge connector conductor of a printed circuit board plugged into the cylindrical back plane. The conductive spiders are stacked in alternating fashion with a plurality of insulating disks, so that each conductive spider is insulated from the others. Corresponding legs of alternative conductive spiders are aligned with each other. The outer conductive leg portions of adjacent conductive spiders are aligned with corresponding contact conductors of a printed circuit board. The outer leg portions extend radially from a common centre and connect to printed circuit boards which are arranged around the circumference of the spiders. The outer leg portions are inserted into contact holes in the female socket portion of a connector, thereby making electrical contact with each respective circuit board. In accordance with the present invention, a parallel system bus structure comprises a plurality of sets of bus conductors each having a plurality of signal conductors of equal length extending radially from a common contact centre, the sets of bus conductors being stacked and spaced apart along an axis; and a plurality of stationary connectors each being connected to selected signal conductors and being adapted to mate with an edge connector of a CPU board, the stationary connectors being arranged around the sets of bus conductors, whereby the structure permits connection between selected signal conductors on each set of bus conductors and selected terminals on each of a plurality of CPU boards, which stand upright in use around the sets of bus conductors, characterized in that the sets of bus conductors are bus wire printed boards, and the stationary connectors are adapted to mate with pin holes (10a,10b,10c) at the edge of a CPU board via L-shaped metals. The present invention provides an improved parallel system bus structure which permits interboard signal paths to be equal and as short as possible regardless of the number of CPU boards used, thereby simplifying signal transmission controlling, and increasing the inter-CPU board communication speed to the maximum possible. Thus all CPU boards can be electrically connected to each other by selected two radial signal conductors. The present invention also provides an improved parallel system bus structure which permits even cooling of all CPU boards used, thereby keeping them at a given constant temperature. Preferably at least one bus wire-printed board is composed of a plurality of layers each bearing a plurality of signal conductors and a common contact centre connected thereto. Thus, signal conductors are provided at an increased density. Each bus wire-printed board may have a dielectric layer bearing a plurality of ground conductors on its undersurface, extending parallel to the signal conductors on its uppersurface so that the signal conductors are shielded. Typically, the bus structure further comprises at least one air conditioning fan above or below the vertical arrangement of said bus wire-printed boards on its central axis. All CPU boards will be evenly cooled and kept at an equal temperature. Inter-CPU board communication will be performed via a group of radial signal conductors on the bus-printed board, which radial signal conductors are connected to the lead conductors of each CPU board. Some examples of the present invention and a known structure are illustrated in the accompanying drawings, in which:- Fig.1 is a perspective view of a radial type of parallel system bus structure according to one embodiment of the present invention; Fig.2 is a schematic diagram showing a series-arrangement of CPU boards connected via a parallel system bus in a multi-microprocessor system; Fig.3 is a perspective view of a CPU board; Fig.4 is a plane view showing the radial arrangement of signal conductors printed on a selected layer of the bus-printed board; Fig.5 is a plane view showing the radial arrangement of ground conductors printed on a selected layer of the bus-printed board; Fig.6 is a perspective view showing signal conductors and corresponding ground conductors in overlying and underlying layers; Fig.7 is a plane view of the bus disk, showing radial arrangements of signal conductors in selected three layers at different levels; Fig.8 is a sectional view of a bus-printed board, showing signal and ground conductors in layers at different levels; Fig.9 is a side view of a vertical stack of bus-printed boards and a CPU board, which are to be connected together; Fig.10 is a plane view of the stack of bus-printed boards and the CPU board; Fig. 11 is a plane view of radial arrangement of signal conductors printed on a selected layer of a bus-printed board; Fig.12 is a plane view of radial arrangement of ground conductors printed on a selected layer of the bus-printed board; and Fig. 13 is a perspective view of a conventional arrangement of CPU boards standing upright and arranged side by side. As regards external buses which are designed for use in micro-processor computor systems, every manufacturing company established standards according to which they make external buses. Preferred embodiments of the present invention will be described as being applied to a Parallel System Bus manufactured by Intel Corp. Such multi-bus was designed for use in a multi-microprocessor system having a plurality of microprocessors built therein. As seen from Fig.2, these microprocessors are connected to each other by a Parallel System Bus 1. There are two kinds of CPU boards to be used in such a multi-microprocessor system, i.e., one ("Single-High Board") equipped with a single board connector 3 on its terminal edge (See Fig. 3), and the other("Double-High Board") equipped with two board connectors on its terminal edge. A board connector 3 has 32 connector pins 4 arranged each in three lines (96 connector pins in total). Fig.4 is a plan view of the upper layer in a three-layer bus-printed board 5, which is made of epoxy resin. Signal conductors are indicated at 6; and terminals for the signal conductors in the upper layer, intermediate layer and lower layer are indicated at 9a, 9b and 9c. Each layer has 20 signal conductors 6 of equal length extending radially from its center common contact 7 at regular angular spaces. As seen from Fig.5, the ground conductors 8 are arranged in the same pattern as the signal conductors 6 so that they may be in registration with the overlying signal conductors 6. Fig.6 shows diagrammatically the manner in which signal conductors 6 and corresponding ground conductors 8 are arranged at different levels in the form of lamination. As shown in Fig.8 a bus-printed board 5 may be composed of three bus layers each having signal and ground conductors (or six sub-layers each having signal or ground conductors). The signal conductors 6 in each layer are arranged offset from the signal conductors 6 in the other layers, and all ground conductors 8 are grounded. Fig.7 shows that the signal conductors 6 in upper layer (solid lines), intermediate layer (dot-and-dash lines) and lower layer (broken lines) are arranged offset from the signal conductors 6 in the other layers. The end of each signal conductor 6 is electrically connected to a terminal 9a, 9b or 9c by soldering and lining its pin hole 10a, 10b or 10C with a soldering material. A bus-printed board has 20 x 3 pin holes for the signal conductors 6 in three layers. Three pin holes 10a, 10b and 10c make up a single set (See Fig.8). In use, twelve bus-printed boards 5 are arranged vertically at regular spaces on four support rods 11, which stand on a frame (not shown). stationary conectors 12 are fixed to the frame, and all terminals of each stationary connector 12 are connected to the pin holes with the aid of L-shaped metals 13. CPU boards 2 standing upright are connected to the bus-printed boards 5 with their connector pins 4 inserted in the pin holes of the stationary connector 12. Then, each set of three pin holes 10a, 10b and 10c receive three pins 4 at same level (See Figs.9 and 10). Each CPU board 2 is held by slidably inserting its upper and lower edges in upper and lower guide slots of the frame (not shown). As seen from Fig.1, a desired number of CPU boards 2 are arranged radially on the circumferences of twelve bus-printed disks 5. Air-conditioning fans 14 and 15 are put above and below the bus-printed disk column. The standard distance between adjacent CPU boards when connected to a Parallel System Bus is 0.8 inches (20.32mm). A longest data bus commercially available is 16.8 inches long. Therefore, twenty CPU boards can be connected to such data bus at standard intervals of 0.8 inches, and if CPU boards of "board-add-on" type (in which type a CPU board has a small board added thereon) are used, a less number of CPU boards are permitted. In contrast, twenty CPU boards of "board-add-on" type can be connected to the circumference of a bus disk bearing spoke-like conductors because these CPU boards are arranged at regular angular intervals, leaving a divergent space between adjacent CPU boads, which divergent space is large enough to accommoadate the extra small board. Figs. 11 and 12 show another pattern of signal conductors 6 and ground conductors 8. As shown, each common center contact 7 is a small ring whose aperture 16 permits insertion of a support rod to hold a bus-printed disk 5. In this particular embodiment the signal path between selected CPU boards cannot be exactly same, but can be substantially twice as long as a radial signal conductor. As may be understood from the above, the radial arrangement of signal conductors in a parallel system bus according to the present invention permits connection of selected CPU boards via equal length of signal path, no matter how many CPU boards may be used. Therefore, no timed control is required in transmission of signals between selected CPU boards via the bus, and accordingly communication speed will be increased to meet highly functional computer's requirements. Signal conductors can be printed on a relatively small disk at an increased density. Accordingly, the space occupied by the bus may be reduced. Parallel arrangement of ground conductors in registration with signal conductors at different levels provides effective electromagnetic shielding, thereby preventing leakage of signals and eliminating adverse effect by noise signals. Air-conditioning fans below and/or above the bus disk column permit even cooling of the CPU boards surrounding the bus disk column to keep them at equal temperature.

Claims: A parallel system bus structure comprising: a plurality of sets of bus conductors (5) each having a plurality of signal conductors (6) of equal length extending radially from a common contact centre (7), the sets of bus conductors being stacked and spaced apart along an axis; and a plurality of stationary connectors (12) each being connected to selected signal conductors and being adapted to mate with an edge connector (3) of a CPU board (2), the stationary connectors being arranged around the sets of bus conductors, whereby the structure permits connection between selected signal conductors on each set of bus conductors and selected terminals on each of a plurality of CPU boards, which stand upright in use around the sets of bus conductors, characterized in that the sets of bus conductors are bus wire printed boards (5), and the stationary connectors (12) are adapted to mate with pin holes (10a,10b,10c) at the edge of a CPU board via L-shaped metals (13). A structure according to claim 1, wherein at least one bus wire-printed board (5) is composed of a plurality of layers each bearing a plurality of signal conductors (6) connected to the common contact centre (7). A structure according to claim 1 or claim 2, wherein each bus wire-printed board (5) has a dielectric layer bearing a plurality of ground conductors (8) on its undersurface, extending parallel to the signal conductors (6) on its upper surface. A structure according to any of the preceding claims, further comprising at least one air conditioning fan (14,15) axially spaced from the bus wire-printed boards (5).

Inventors: TAKASHIMA TOKUHEI, TAKASHIMA, TOKUHEI
Applicants: GRAPHICO CORP, GRAPHICO CO. LTD.
Application year: 1990
Main classification: H05K7
IPC codes: G06F1, G06F13, G06F15, H05K1, H05K7