Abstract:
A general purpose computer apparatus including a central processing unit, a main memory and a system bus. The general purpose computer apparatus further includes means for interfacing the central processing unit to the system bus and means for interfacing the central processing unit to an I/O bus. A housing encloses the central processing unit, the main memory and the means for interfacing, with the housing having a mechanical form factor corresponding to a disk drive housing.

Description:
This application is a continuation of application Ser. No. 08/092,622, filed Jul. 16, 1993. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to computer systems and more particularly to clustered computer systems. 
   As is known in the art, a computer system is generally comprised of a central processing unit (CPU), a memory unit, at least one input/output device, and a bus which is used to connect the aforementioned devices. The computer is housed in a cabinet which contains a power supply to supply power for the various components of the computer. In operation, the central processing unit fetches and decodes incoming instructions, executes commands, and manipulates data, while the memory unit, which is composed of multiple storage locations, stores data to be used by the CPU. The I/O device is generally used to input data to and output data from the computer system. Typical types of I/O devices include printers, keyboards, displays and mass storage units such as disk drives etc. These devices are often interfaced to the computer system with an I/O interface controller circuit. 
   Often, a user&#39;s processing needs will grow beyond the capabilities of a single CPU. In an effort to meet these new processing needs, computers are typically clustered to make a plurality of CPUs available for processing. A clustered computer system is an integrated group of computers that communicate over a high-speed communication path. The clustered computer system acts as a single system to users. That is, clustered computer systems are characterized by a high degree of transparent resource sharing, which includes access by each individual computer system to storage located anywhere in the clustered system, and increased processing throughput. 
   In a typical cluster, there are two or more CPUs sharing inter alia at least one common system disk. Using multiple CPUs in a clustered configuration enables processing time on the CPUs to be used more efficiently. Thus, it affords the user better performance when jobs are run on a clustered system. 
   At least one additional general purpose computer is necessary to provide a clustered configuration for a computer system. Depending upon the characteristics of an existing system it may be possible to acquire an additional CPU and associated cabinet and power supply and interconnect these devices with the existing equipment. The two systems are connected through the additional cables and harnessing and are configured using software to behave as a clustered computer system. While the existing equipment and acquired general purpose computer system will provide a clustered computer system there are several drawbacks to this approach. For example, included with each general purpose computer system is a power supply and the cabinet as well as additional hardware such as cables and harnessing to connect the two computer systems. Clustering computer systems using this approach provides a redundancy in the hardware of the computer system, but at a substantial increase in cost particularly for the mechanical components necessary to provide the clustered system. Moreover, by providing separate cabinets, longer cables and harnesses are needed to interconnect the systems. This limits the maximum number of systems which can be interconnected, particularly for executing bus specification protocols, due to electrical timing and parameter considerations. 
   Another option available to provide additional processing power is multiprocessing. A single processing board can be used which includes multiple CPUs. This option however is not only costly but it assumes the user has foreseen a future need for an increase in processing power. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a general purpose computer apparatus includes a central processing unit, a main memory, and a system bus. The general purpose computer apparatus further includes means for interfacing the central processing unit to the system bus and means for interfacing the central processing unit to an I/O bus. The general purpose computer system further includes a housing enclosing the central processing unit, the main memory and the means for interfacing with the housing having a mechanical form factor corresponding to a disk drive housing. With such an arrangement, the general purpose computer apparatus is housed in a chassis or housing which can be disposed within a disk drive slot of a standard general purpose computer cabinet. By appropriate interconnect and configuration of the apparatus with a second general purpose computer in the general purpose computer cabinet a clustered computer system can be provided. 
   In accordance with a further aspect of the present invention, a computer system includes a cabinet having at least one slot for receiving a disk drive, and a first general purpose computer apparatus disposed in the cabinet. The first general purpose computer apparatus includes a first central processing unit, a system bus, and an I/O interface module coupled to said system bus for interfacing said system bus to an I/O bus. The computer system further includes a second general purpose computer apparatus which includes a second central processing unit, a main memory, and means for interfacing the second general purpose computer apparatus to the first general purpose computer apparatus. The second general purpose computer apparatus further includes a housing enclosing the second general purpose computer apparatus, the housing having a mechanical form factor corresponding to the slot for receiving a disk drive, with the housing disposed in the slot. With such an arrangement a clustered computer system configuration may be provided by appropriate interconnect and configuration of the second general purpose computer apparatus with the first general purpose computer in the general purpose computer cabinet while saving the cost of an additional cabinet, power supply, cabling and harnessing. In addition, since the length of cabling will in general be shorter than prior approaches, more systems can be clustered on one bus. For example, if the systems are clustered over a DSSI bus, a total of eight systems may be clustered without violating electrical specifications for DSSI bus clusters rather than the maximum of three systems when the systems are housed in separate cabinets and longer lengths of cabling are necessary to interconnect the systems. 
   In accordance with a further aspect of the present invention, a computer system includes a cabinet for housing the computer system, the cabinet having a panel with at least two openings in the panel of the cabinet. The computer system further includes a power supply disposed within the cabinet and a first general purpose computer disposed within the cabinet. The first general purpose computer further includes a first central processing unit module, including a central processing unit, a main memory, an I/O adapter interface, and a system bus coupling the first central processing unit module to the main memory and the I/O adapter interface. The computer system further includes a disk drive disposed in a first one of the openings in the panel of the cabinet and a second general purpose central processing unit module disposed in a second one of the openings in the panel of the cabinet and coupled to the cabinet by the corresponding receiving means. The second general purpose central processing unit module further includes a control panel having at least one switch which is used to reboot the second central processing unit module. The first central processing unit module and the second central processing unit module receive power from the power supply. With such an arrangement the existing equipment may be connected to the general purpose central processing unit module to provide a multiprocessing system thus, saving the user the cost of a complete multiprocessing system as well as in some cases protecting an investment made in existing equipment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features of the invention will now become more apparent by reference to the following description taken in connection with the accompanying drawings in which: 
       FIG. 1  is a block diagram of a general purpose, clustered computer system; 
       FIG. 2  is an isometric view of a computer system cabinet housing the general purpose, clustered computer system of  FIG. 1 ; 
       FIG. 3  is an exploded view of a general purpose computer brick; 
       FIG. 4  is an isometric cutaway view of the general purpose computer brick of  FIG. 3  showing inner components of the brick; 
       FIG. 5  is a block diagram representing the partitioning of the modules of the general purpose computer brick; and 
       FIG. 6  is an isometric view of the general purpose computer brick depicting a relationship between the apertures in the enclosure of the brick and notches in printed circuit boards disposed in the enclosure. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIG. 1 , a general purpose, clustered computer system  10  is shown to include a general purpose computer  11  having inter alia a Central Processing Unit (CPU)  12 , a system memory  13 , I/O  16  and an I/O bus adapter  15  all interconnected via a system bus  14 . CPU  12  typically includes a microprocessor device, interface circuits and timing and control circuits and is used to process computer instructions, generally fetched from system memory  13 , in a predetermined manner to complete some computer processing task. System memory  13  typically includes a plurality of integrated circuit memory devices such as dynamic random access memory (DRAM) or static random access memory (SRAM) which provide main data storage for the CPU. The I/O bus adapter  15  is further coupled to two disk drives  17  and  18  through an I/O bus  20 . 
   The general purpose, clustered computer system further includes a second general purpose computer  19  including a CPU  21 , a system memory  22 , I/O  23  and an I/O bus adapter  24  each communicating through a system bus  25 . In general the second general purpose computer system  19  provides similar functionality as general purpose computer system  11 . Further included in the second general purpose computer  19  is an operator control panel  26  which provides an operator control over the second general purpose computer  19 . The clustered general purpose computer is also shown to include a single power supply  27 , which provides all appropriate voltages such as five volts for the logic devices and twelve volts for the electro-mechanical devices in the disk drive. That is the power supply here supplying power to each module of the first general purpose computer as well as to each of the disk drives and each module of the second general purpose computer  19 . General purpose computer  11  and general purpose computer  19  are logically connected through a Digital Storage System Interconnect (DSSI) Bus  28  here referred to as DSSI bus — 0. 
   Referring now to  FIG. 2 , a system cabinet  30  to house the general purpose, clustered computer system of  FIG. 1  is shown. The first general purpose computer system  11  and power supply  27  are housed within the lower portion of the cabinet here depicted by modules  35   a - 35   g . The power supply  27  is depicted here as being located in the right hand portion  36 , as shown. The cabinet  30  further has openings to accommodate here, three disk drives. Housed in one of the disk drive openings is the second general purpose computer  19  including the CPU module, the memory module, the system bus, and the I/O adapter interface as discussed above appropriately packaged  32 . Here, shown housed in one of the remaining disk drive openings, is a disk drive  31 . The third disk drive slot  33  is shown empty. Also shown included in the system cabinet  30  is a tape drive  34 . The packaged  32 , second general purpose computer system  19  of  FIG. 1 , is located within the disk drive opening and is physically and logically connected through the standard disk drive connections, including power and an I/O bus capable of supporting CPU to CPU communication protocol. Examples of bus protocols include a system bus protocol, a network protocol and an I/O bus protocol. Preferably, the bus protocol is the Digital Storage System Interconnect (DSSI). 
   A DSSI bus is a general purpose communication bus. The DSSI bus is used to connect host computers and storage devices. It is similar in function to a Computer Interconnect (CI) bus protocol which is used for interconnecting medium to large computer systems into clusters. The DSSI bus, like the CI bus, operates using the System Communication Architecture protocols. The DSSI bus is the preferable bus because it operates at a high level thus handling error conditions more effectively. Because the electrical specifications for a DSSI bus cluster are very stringent regarding the lengths of the electrical paths, the maximum number of nodes on a DSSI bus cluster is three when a typical configuration using separate cabinets for each system is used. By connecting additional general purpose computer systems through the DSSI ports in the disk drive slots, shorter electrical paths result, thus allowing the maximum number of general purpose computer systems which may be connected through this process to increase up to eight. Through these connections and some additional clustering software, the general purpose computer system apparatus is connected in a cluster configuration with the general purpose computer housed within the main cabinet. 
   Referring now to  FIG. 3 , the second general purpose computer system  19  is packaged in a configuration adapted to be mounted in a standard 5¼ inch disk drive opening. The enclosure for the second general purpose computer  19  is shown to include a vented side panel  42   a  which allows air flow through the apparatus. A portion of the panel  42   b  is bent at an angle orthogonal to the air vented portion of the panel and includes five apertures  54   a - 54   e  through which the second general purpose computer system  19  receives connections from the general purpose computer system  11  for DSSI bus — 0, a Small Computer System Interconnect (SCSI) bus and a Q bus. Through two of the apertures  54   b ,  54   c  the second general purpose computer system also receives power from the power supply  27 . The opposing side of the general purpose computer apparatus is shown as a solid metal chassis having a pair of side panels  41   a ,  41   b  bent at an angle such that the panels  41   a ,  41   b  are mutually parallel and orthogonal to the base member  41   c . The side panels  41   a ,  41   b  have guides  55  which will position here three printed circuit boards  43 ,  44 ,  45  disposed within the metal enclosure. Also located on these two side panels  41   a ,  41   b  are three pairs of rectangular apertures  52   a′ ,  52   a″ ,  52   b′ ,  52   b″ ,  52   c′ ,  52   c″.    
   At a first end of the general purpose computer apparatus  40  is an area  56  through which access is available to a locking connector disposed within the metal enclosure of the general purpose computer apparatus  40 . This locking connector accepts a ribbon cable input located on the back of the control panel  26 . Secured to two of the sides of the metal enclosure is additional air vented bracketing  50 ,  51  which allows the packaged general purpose computer  32  to be inserted into a disk drive opening in a system cabinet  30  as shown in FIG.  2 . Further included at one end of the metal enclosure are connectors  46  which the printed circuit boards are plugged into. Additional connectors are found at the opposite end of the CPU module  57 , a mate and lock connector  48  to connect to the power supply  27  and a ribbon cable connector  47  with locking tabs to connect to the DSSI bus — 0  28  and the SCSI bus of general purpose computer system  11 . The opposing end of each of these connectors plugs into a paddle card  49  which physically connects to the backplane within the disk drive slot and logically connects to the SCSI bus and the DSSI bus — 0  28  of general purpose computer system  11 . Shown is a typical configuration including two DSSI buses, a SCSI bus, a Q bus which is a general purpose I/O bus and an NI bus or ETHERNET bus which is a network bus as will be mentioned. Other configurations of course could be used, provided a bus is made available to interconnect the first general purpose computer to the second general purpose computer. 
   Referring now to  FIG. 4  the assembled general purpose computer  19  packaged as a computer “brick”  32  is shown to include a CPU module  21 , an I/O module  23  and eight single inline memory modules plugged at an angle into a memory carrier  22 . The CPU module  21  is partitioned to contain the logic for the CPU, the DSSI bus — 0  28  and the network interconnect. The I/O module  23  is partitioned to include the logic for I/O operations, DSSI bus — 1 and Q bus. The CPU module  21 , the I/O module  23  and the memory carrier  22  are each provided with notches  53   a′ ,  53   a″ ,  53   b′ .  53   b″ ,  53   c′ ,  53   c″  on the edges of the printed circuit board to be used in removing the individual boards from the enclosure as will be described. 
   Cabling to connect the general purpose computer brick to the existing general purpose computer system housed within the existing cabinet is fed through five apertures  54   a - 54   e  at one end of the general purpose computer brick&#39;s enclosure. Connections are made to power, DSSI bus — 0  28 , SCSI and Q bus through these five apertures  54   a - 54   e . On the opposite end of the brick from these apertures, the operator control panel  26  is connected using a high density ribbon cable  61  into a connector on the general purpose computer brick which includes locking tabs. The operator control panel  26  includes a network interconnect BNC connector  60  here for an NI or ETHERNET bus and a console port. Also included are a reset button (reboot)  66 , a halt button  65  and a halt enable switch  62 . Two high density dual in-line (DIN) connectors  65 ,  66  are also included through which peripherals may be connected to the general purpose computer brick&#39;s  32  DSSI bus — 1. The operator control panel also includes a diagnostic display  67  to display any errors the general purpose computer brick  32  might encounter. 
   Referring now to  FIG. 5 , the partitioning of the CPU  21 , the I/O  23  and the memory modules  22  of  FIG. 4  are shown to include the system microprocessor  70 , I/O  71  and memory control  72  and a Single Host Adapter Chip (SHAC) for the DSSI bus — 0 interface  73  and a Second Generation Ethernet Chip (SGEC) Network Interconnect interface  74  in the CPU module  21 . The memory control  72  on the CPU module  21  is connected into the memory module  22  which includes the memory carrier  75  and the single inline memory modules  76   a - 76   h  which provide the main system memory. The I/O control  71  of the CPU module  21  is connected into the I/O module  23  which is partitioned to include the read only memory for the bootstrap and diagnostics code  77 . Further included in the partitioning of the I/O module  23  is the system support chip  78  and the non-volatile Random Access Memory  79 . Interface logic is also included for an SCSI Bus  81 , a Q bus  82  and a SHAC for DSSI Bus 1  80  on the I/O module  23 . 
   Referring now to  FIG. 6 , the brick is shown to include pairs of rectangular apertures  52   a′ ,  52   a″  in proximity to pairs of notches  53   b′ ,  53   b″  on edges of the printed circuit boards  21 ,  22 ,  23 . When the printed circuit boards  21 ,  22 ,  23  are in place within the enclosure of the general purpose computer brick  32  the pair of notches  53   a′ ,  53   a″  on opposing edges of the circuit boards are aligned with apertures  52   a′ ,  52   a″  within the sides of the brick  32 . Here the apertures  52   a′ ,  52   a″  are rectangular but of course other shaped apertures could be used. Two flat-headed screwdrivers (not shown) are inserted through the rectangular shaped apertures  52   a′ ,  52   a″  into one of the pair of corresponding notches  53   a′ ,  53   a″  in the circuit board  21  and pressure is placed against the side of the notch to pry or pop the circuit board from its connector. Because of the distance the circuit board must travel in order to be completely freed from the connector, it is preferred to have two rectangular apertures as well as two notches provided in order that the necessary travel may be achieved. The notches are placed in the circuit boards such that when the circuit board is in place within the enclosure half of one of the notches is visible through the rectangular aperture and the second notch is hidden behind the space between the two apertures. 
   Having described preferred embodiments of the invention, it will now become apparent to those of skill in the art that other embodiments incorporating its concepts may be provided. It is felt therefore that this invention should not be limited to the disclosed embodiments but rather should be limited only by the spirit and scope of the appended claims.