Abstract:
The present invention includes a computer bus rack having a circuit board for accommodating a plurality of stand-alone computers. The circuit board has a front side and a back side, and the rack comprises a first plurality of slots coupled to the front side, and a second plurality of slots coupled to the back side. The first and second plurality of slots are arranged such that corresponding ones of the first and second plurality of slots are in alignment together. Also, a plurality of connectors are affixed to the circuit board in alignment with the first and second plurality of slots, and have respective pass-through connector-pins that extend into each of the first and second slots, wherein certain ones of the connector-pins allocated to carry power signals are commonly connected for each of the plurality of connectors, and remaining ones of the connector-pins with respect to a particular slot are electrically isolated from connector-pins with respect to another slot on the same one of the front side and the back side. Because the connector-pins of the slots in the present invention are not electrically connected to each other, except for the connector-pins carrying power signals, each slot acts as an isolated bus. This allows an independent stand-alone computer to be coupled to each slot of the circuit board.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a Compact Peripheral Component Interconnect (“CPCI”) computer system. More specifically, the present invention relates to a bus rack for accommodating a plurality of stand-alone computers. 
     2. Description of Related Art 
     Compact Peripheral Component Interconnect (“CPCI”) is a high performance industrial bus based on the standard PCI electrical specification in rugged  3 U or  6 U Eurocard packaging. CPCI is intended for application in telecommunications, computer telephony, real-time machine control, industrial automation, real-time data acquisition, instrumentation, military systems or any other application requiring high speed computing, modular and robust packaging design, and long term manufacturer support. Because of its extremely high speed and bandwidth, the CPCI bus is particularly well suited for many high-speed data communication applications such as servers, routers, converters, and switches. 
     Compared to standard desktop PCI, CPCI supports twice as many PCI slots (8 versus 4) and offers a packaging scheme that is much better suited for use in industrial applications. Conventional CPCI cards are designed for front loading and removal from a card cage. The cards are firmly held in position by their connector, card guides on both sides, and a faceplate that solidly screws into the card cage. Cards are mounted vertically allowing for natural or forced convection for cooling. Also, the pin-and-socket connector of the CPCI card is significantly more reliable and has better shock and vibration characteristics than the card edge connector of the standard PCI cards. 
     Conventional CPCI defines a backplane environment that is limited to eight slots. One slot, the system slot, provides the clocking, arbitration, configuration, and interrupt processing for the other seven slots. Accordingly, the conventional CPCI system is limited to only one stand-alone computer since only the system slot is adapted to receive a CPU daughter card, and the other peripheral slots are reserved for peripheral daughter cards. However, many applications require larger systems so that it would be advantageous to provide multiple stand-alone computers in a CPCI system. 
     SUMMARY OF THE INVENTION 
     The present invention provides a computer bus rack that is able to accommodate a plurality of stand-alone computers, which are comprised of CPU cards that are inserted into the slots of the bus rack. The inserted CPU cards operate independently with respect to one another so that there is independent operation of the stand-alone computers. By allowing for the independent operation of multiple stand-alone computers, the present invention is able to provide the advantages of, for example, pure multitasking, parallel processing, redundancy, mirroring, back-up, and more computing power for a given board size. 
     The computer bus rack includes a circuit board, which is called a midplane in the present invention. The circuit board is referred to as a backplane or midplane depending on its placement in the computer chassis, which is significant. For example, if the circuit board is located at the back of the chassis so that it is a backplane, then it will allow the insertion of “add-on” cards only from the front side, whereas a circuit board that is located at the middle of the chassis allows for the insertion of add-on cards from both sides--front and back. In the present invention, the circuit board is referred to as the midplane, while the conventional circuit board is referred to as the backplane. 
     In an embodiment of the invention, a computer bus rack has a circuit board for accommodating a plurality of stand-alone computers. The circuit board has a front side and a back side, and the rack comprises a first plurality of slots coupled to the front side, and a second plurality of slots coupled to said back side. The first and second of slots are arranged such that corresponding ones of the first and second slots are in alignment together so as to be back to back. Also, a plurality of connectors are affixed to the circuit board in alignment with the first and second plurality of slots, and have respective pass-through connector-pins that extend into each of the first and second slots, wherein certain ones of the connector-pins allocated to carry power signals are commonly connected for each of the plurality of connectors, and remaining ones of the connector-pins with respect to a particular slot are electrically isolated from connector-pins with respect to another slot on the same one of the front side and the back side. 
     In another embodiment of the invention, a computer system has a plurality of stand-alone computers coupled to a common circuit board, with the circuit board having a front side and a back side. The front and back sides have a plurality of slots including a plurality of connectors, with the computer system comprising a plurality of CPU daughter cards pluggable in the slots of the front side and corresponding I/O transition cards pluggable in the slots of the back side. Power signals are shared by each of the plurality of connectors of each slot, and I/O signals are only transmitted between the daughter cards on the front side and the corresponding I/O transition card on the back side. 
     Because the connector-pins of the slots in the midplane are not electrically connected to one another, except for the power signals, each is an “isolated” bus. For example, for a given slot, only certain connector-pins transmit I/O signals, and the other connector-pins carry power signals. The connector-pins that transmit I/O signals are isolated electrically from the connector-pins of the other slots of the circuit board, whereas the connector-pins that transmit power signals are electrically connected to the connector-pins of the other slots. Thus, when a CPU card is inserted in a slot of the midplane, the I/O signals are only transmitted between the CPU card and the I/O transition card that is inserted in the corresponding slot that is on the other side of the midplane, whereas the power signals are shared with all the other slots. This allows multiple CPU cards to be inserted in the slots of the same midplane, yet operate independently. Thus, a plurality of stand-alone computers can be provided in a single midplane of the present invention. Accordingly, the midplane is able to accommodate stand-alone computers that may be used independently so as to realize the advantages of, for example, pure multitasking, parallel processing, redundancy, mirroring, back-up, or more computing power for a given board size. 
     A more complete understanding of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiments. Reference will be made to the appended sheets of drawings, which will first be described briefly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a conventional CPCI chassis system; 
     FIG. 2 shows the form factor that is defined for the CPCI daughter card; 
     FIG. 3 is a front view of a conventional  3 U backplane having eight slots with two connectors each; 
     FIG.  4 ( a ) shows a front view of a conventional CPCI backplane in the  6 U form factor; 
     FIG.  4 ( b ) shows a back view of a conventional CPCI backplane in the  6 U form factor; 
     FIG. 5 shows a side view of the conventional backplane of FIGS.  4 ( a ) and  4 ( b ); 
     FIG.  6 ( a ) shows a front view of a midplane according to an embodiment of the invention; 
     FIG.  6 ( b ) shows a back view of a midplane according to an embodiment of the invention; 
     FIG.  6 ( c ) shows a side view of a chassis system according to an embodiment of the invention; 
     FIG. 7 shows a side view of the midplane of FIGS.  6 ( a ) and  6 ( b ); 
     FIG.  7 ( a ) shows a cross-section of the midplane of FIG. 7 taken across the line  7 ( a )— 7 ( a ); 
     FIG. 8 shows a stand-alone computer in a slot of the midplane of FIG. 7; 
     FIGS.  9 ( a ) and  9 ( b ) show the arrangement of the connector-pins of the front side and back side connectors according to an embodiment of the invention; and 
     FIG. 10 shows the components of an I/O transition card according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides a bus rack including a circuit board that is able to accommodate a plurality of stand-alone computers. Advantages of providing multiple stand-alone computers coupled to a single circuit board include multitasking, parallel processing, redundancy, mirroring, back-up, and more computing power for a given board size, which is required for more powerful applications. 
     Referring to FIG. 1, there is shown a perspective view of a conventional CPCI chassis system. The chassis system  100  includes a CPCI circuit board referred to in the conventional CPCI system as a passive backplane  102  since the circuit board is located at the back of the chassis  100  and add-on cards can only be inserted from the front of the chassis  100 . On the front side of the backplane  102  are slots provided with connectors  104 . In the conventional chassis system  100  that is shown, a daughter card  108  may be inserted into appropriate slots and mate with the connectors  104 . For proper insertion of the daughter cards  108  into the slots, card guides  110  are provided. This conventional chassis system  100  provides front removable daughter cards and unobstructed cooling across the entire set of daughter cards  108 . 
     Referring to FIG. 2, there is shown the form factor defined for the CPCI daughter card, which is based on the Eurocard industry standard. As shown in FIG. 2, the daughter card  200  has a front plate interface  202  and ejector/injector handles  204 . The front plate interface  202  is consistent with Eurocard packaging and is compliant with IEEE 1101.1 or IEEE 1101.10. The ejector/injector handles should also be compliant with IEEE 1101.1. One ejector/injector handle  204  is used for  3 U daughter cards, and two ejector/injector handles  204  are used for  6 U daughter cards. Note that the connectors  104   a - 104   e  are numbered starting from the bottom connector  104   a , and that both  3 U and  6 U daughter card sizes are defined, as described below. 
     The dimensions of the  3 U form factor are approximately 160.00 mm by approximately 100.00 mm, and the dimensions of the  6 U form factor are approximately 160.00 mm by approximately 233.35 mm. The  3 U form factor includes two 2 mm connectors  104   a - 104   b , and is the minimum as it accommodates the full 64 bit CPCI bus. Specifically, the  104   a  connectors are reserved to carry the signals required to support the 32-bit PCI bus, hence no other signals may be carried in any of the pins of this connector. Optionally, the  104   a  connectors may have a reserved key area that can that be provided with a connector “key”, which is a pluggable plastic piece that comes in different shapes and sizes, so that the add-on card can only mate with an appropriately keyed slot. The  104 b connectors are defined to facilitate 64-bit transfers or for rear panel I/O in the  3 U form factor. The  104   c |- 104   e  connectors are available for  6 U systems as shown in FIG.  1 . The  6 U form factor includes the two connectors  104   a - 104   b  of the  3 U form factor, and three additional 2 mm connectors  104   c - 104   e . In other words, the  3 U form factor includes connectors  104   a - 104   b , and the  6 U form factor includes connectors  104   a - 104   e . The three additional connectors  104   c - 104   e  of the  6 U form factor can be used for secondary buses (i.e., Signal Computing System Architecture (SCSA) or MultiVendor Integration Protocol (MVIP) telephony buses), bridges to other buses (i.e., Virtual Machine Environment (VME) or Small Computer System Interface (SCSI)), or for user specific applications. Note that the CPCI specification defines the locations for all the connectors  104   a - 104   e , but only the signal-pin assignments for the CPCI bus portion  104   a  and  104   b  are defined. The remaining connectors are the subjects of additional specification efforts, or can be user defined for specific applications, as described above. 
     Referring to FIG. 3, there is shown a front view of a conventional  3 U backplane having eight slots with two connectors each. A CPCI system is composed of one or more CPCI bus segments, where each bus segment includes up to eight CPCI card slots. Each CPCI bus segment consists of one system slot  302 , and up to seven peripheral slots  304   a - 304   g . The CPCI daughter card for the system slot  302  provides arbitration, clock distribution, and reset functions for the CPCI peripheral cards on the bus segment. The peripheral slots  304   a - 304   g  may contain simple cards, intelligent slaves or PCI bus masters. 
     The connectors  308   a ,  308   b  have connector-pins  306  that project in a direction perpendicular to the backplane  300 , and are designed to mate with the front side “active” daughter cards  108  (see FIG.  1 ), and “pass-through” its relevant interconnect signals to mate with the rear side “passive” input/output (I/O) card(s) (not shown). In other words, the connector-pins  306  allow the interconnected signals to pass-through from the active front side daughter cards to the rear side passive I/O cards. 
     Referring to FIGS.  4 ( a ) and  4 ( b ), there are shown a front and back view of a conventional CPCI backplane in the  6 U form factor, respectively. In FIG.  4 ( a ), four slots  402   a - 402   d  are provided on the front side  400   a  of the backplane  400 . In FIG.  4 ( b ), four slots  406   a - 406   d  are provided on the back side  400   b  of the backplane  400 . Note that in both FIGS.  4 ( a ) and  4 ( b ) only four slots are provided instead of eight slots as in FIG.  3 . Further, it is important to note that each of the slots  402   a - 402   d  on the front side  400   a  have five connectors  404   a - 404   e  while each of the slots  406   a - 406   d  on the back side  400   b  have only four connectors  408   b - 408   e . This is because, as in the  3 U form factor of the conventional CPCI system, the  404   a  connectors are provided for 32 bit PCI and connector keying. Thus, they do not have I/O connectors to their rear. Accordingly, the daughter cards that are inserted in the front side slots  402   a - 402   d  only transmit signals to the rear transition cards that are inserted in the back side slots  406   a - 406   d  through front side connectors  404   b - 404   e.    
     Referring to FIG. 5, there is shown a side view of the conventional backplane of FIGS.  4 ( a ) and  4 ( b ). As shown in FIG. 5, slot  402   d  on the front side  400   a  and slot  406   d  on the back side  400   b  are arranged to be substantially aligned so as to be back to back. Further, slot  402   c  on the front side  400   a  and slot  406   c  on the backside  400   b  are arranged to be substantially aligned, and so on. Accordingly, the front side connectors  404   b - 404   e  are arranged back-to-back with the back side connectors  408   b - 408   e . Note that the front side connector  404   a  does not have a corresponding back side connector. It is important to note that the system slot  402   a  is adapted to receive the CPU daughter card, and the signals from the system slot  402   a  are then transmitted to corresponding connector-pins of the peripheral slots  402   b - 402   d . However, a conventional CPCI system does not allow multiple stand-alone computers to be inserted in the multiple slots of the CPCI board. 
     The present invention has the advantage of being able to accommodate a standalone computer for each slot of the CPCI board. Referring to FIGS.  6 ( a ) and  6 ( b ), there are shown a front and back view, respectively, of a CPCI midplane according to an embodiment of the invention. In the present invention, the CPCI circuit board  600  is referred to as the midplane because it is located in the middle of the chassis, and is able to have add-on cards inserted from the front and back. For example, referring to FIG.  6 ( c ), which shows a side view of a chassis according to an embodiment of the invention, the midplane  600  is located at the middle of the chassis  610  having top and bottom guides  614 ,  612 . However, it should be noted that the CPCI circuit board of the present invention may be located in any suitable place on the CPCI chassis. As shown in FIG.  6 ( a ), on the front side  600   a  of the midplane  600 , there are provided four slots  602   a - 602   d  having five connectors  604   a - 604   e  each. As shown in FIG.  6 ( b ), on the back side  600   b  of the midplane  600 , there are also provided four slots  606   a - 606   d  having four connectors  608   b - 608   e  each. Note that although only four slots are shown on the front side  600   a  and back side  600   b  of the midplane  600 , the present invention may include more slots or fewer slots. 
     Referring to FIG. 7, there is shown a side view of the midplane of FIGS.  6 ( a ) and  6 ( b ). As illustrated in FIG. 7, the slot  602   d  on the front side  600   a  and slot  606   d  on the back side  600   b  are arranged to be substantially aligned so as to be back to back. Further, slot  602   c  on the front side  600   a  and slot  606   c  on the back side  600   b  are arranged to be substantially aligned so as to be back-to-back, and so on. Accordingly, the signals from the CPCI daughter cards that are inserted in the front side slots are transmitted to the I/O cards that are inserted in the back side slots from connectors  604   b - 604   e  to connectors  608   b - 608   e , respectively. Note that in the present invention, each slot  602   a - 602   d  on the front side  600   a  is adapted to receive a CPU card so that signals being transmitted on connector-pins of one slot are not shared with the connector-pins of the other slots on the same side, except for the power signals. For example, referring to FIG.  7 ( a ), there is shown a cross-section of the mid-plane of FIG. 7 across the line  7 ( a )— 7 ( a ), and which shows the signal traces of the midplane  600 . FIG.  7 ( a ) shows slots  602   c  and  602   d  having connectors  604   a - 604   e , respectively. As shown in FIG.  7 ( a ), connector  604   e  of both slots  602   c ,  602   d  have connector-pins  702  represented by +&#39;s which correspond to I/O signal pins, and connector pins  704  represented by dots, which correspond to power signal pins. For illustration, signal traces  706  connect the connector-pins  704  of slot  602   c  to corresponding connector-pins  704  of slot  602   d , while the connector-pins  702  are not electrically connected to any corresponding connector-pins of any different slot. In other words, the signal traces  706  on the midplane  600  only electrically connect the connector-pins  704  that are defined to receive the power signals, and not the connector-pins  702  that are defined for I/O signals. 
     Because the connector-pins  702  of the slots  602   c ,  602   d  in the midplane  600  are not electrically connected to one another, except for the power signal connector-pins  704 , each slot  602   c ,  602   d  acts as an “isolated” bus. Thus, when a CPU card is inserted in a slot  602   a - 602   d  of the midplane  600 , the I/O signals are only transmitted between the CPU card and the I/O transition card that is inserted in the corresponding slot that is on the other side of the midplane  600 , whereas the power signals are shared with all the other slots  602   a - 602   d . This allows multiple CPU cards to be inserted in the slots  602   a - 602   d  of the same midplane  600 , yet operate independently. Thus, a plurality of standalone computers can be provided in a single midplane  600  of the present invention, allowing for advantages such as pure multitasking, parallel processing, redundancy, mirroring, back-up, and more computing power within a given board size. 
     Referring to FIG. 8, there is shown a stand-alone computer in a slot of the midplane of FIG.  7 . As shown in FIG. 8, a CPU daughter card  802  is inserted in slot  602   d  of the midplane  600 , and an I/O transition card  804  is inserted in slot  606   d  of the midplane  600 . By having the cards  802 ,  804  inserted in the slots  602   d ,  606   d , respectively, a stand-alone computer  800  is provided in a single slot of the midplane  600 . Further, by inserting additional CPU daughter cards and I/O transition cards in the other slots  602   a - 602   c ,  606   a - 606   c , respectively, of the midplane  600 , a plurality of stand-alone computers  800  can be connected to the midplane  600 . 
     Referring to FIGS.  9 ( a ) and  9 ( b ), there are shown the arrangement of the connector-pins of the front side and back side connectors according to an embodiment of the invention. As shown in FIGS.  9 ( a ) and  9 ( b ), the connector  604   a  and connector  608   a  have a column and row arrangement of connector-pins  900 . Note that the arrangement of the connector-pins of the back side connector  608   a  is a mirror image of the arrangement of the connector-pins of the front side connector  604   a . For example, when the slot  602   d  of the front side  600   a  is aligned so as to be back to back with the slot  606   d  of the back side  600   b , connector-pin  900  located at column z row 2 of the front side connector  604   b  is the same connector-pin  900  located at column z, row 2 of the back side connector  608   b . Thus, the connector-pins  900  of connectors  604   b  and  608   b  are straight pass-through pins. Similarly, the connectors  604   b - 604   e  also share corresponding connector-pins with connectors  608   b - 608   e , respectively. Accordingly, the connector-pins  900  are designed to mate with the front side CPU cards and pass-through the relevant interconnected signals to mate with the rear side I/O transition cards. 
     As described above, the present invention does not interconnect the connector-pins of a slot with the connector-pins of a different slot on the same side of the midplane. Thus, except for the power signals, signals in one slot are isolated from the signals in other slots on the same side of the midplane. Accordingly, on the front side  600   a  of the midplane  600 , CPU cards are pluggable, and on the back side  600   b , I/O transition cards having all of the I/O circuitry and electronics are pluggable. Thus, each CPU card and its corresponding I/O transition card comprise a stand-alone computer, and the midplane  600  is able to accommodate multiple stand-alone computers. Note that the rear I/O transition cards that are pluggable into the back side slots are intelligent cards, and include a mass storage device such as a hard disk  1002 , and may further include other components such as Ethernet controllers  1004 , a serial port  1006 , a parallel port  1008 , a video controller or other types of controllers  1010 , as shown in FIG.  10 . 
     Having thus described different embodiments of the present invention, it should be apparent to those skilled in the art that certain advantages which may be achieved by the present invention. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made within the scope and spirit of the present invention. For example, a CPCI midplane has been illustrated, but it should be apparent that the inventive concepts described above would be equally applicable to other types of circuit boards, computer systems or computer busses. The invention is further defined by the following claims.