Fault tolerant system and method utilizing the peripheral components interconnection bus monitoring card

[0002] This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for FAULT TOLERANT SYSTEM UTILIZING THE PERIPHERAL COMPONENTS INTERCONNECTION BUS MONITORING CARD earlier filed in the Korean Industrial Property Office on Jan. 22^NDof 1998 and there duly assigned Ser. No. 1911/1998.

[0003] 1. Technical Field

[0004] The present invention relates to a fault detection apparatus and method utilizing a PCI (peripheral components interconnection) bus monitoring card. More specifically, the present invention is related to an apparatus and method for guaranteeing the integrity of the PCI bus by connecting a plurality of general purpose computers using a PCI bus and comparing the PCI bus signals between or among them.

[0005] 2. Related Art

[0006] Typically, fault detection systems necessarily have their own central processing unit (CPU) boards or their own input/output buses. This leads to several disadvantages: an increase in design problems; increase in the time to develop new or modified systems; increased complexity of such systems; greater cost in developing and producing such systems; and increased probability of system malfunction or failure.

[0007] Exemplars of recent efforts in the art include U.S. Pat. No. 5,822,512 for Switching Control in a Fault Tolerant System issued to Goodrum et al. The aforementioned patent is different from the present invention.

[0008] It is an object of the present invention to provide an apparatus and method for detecting fault, without providing an exclusive CPU board or input/output bus to detect fault. Rather, a PCI monitoring card is appended to the general purpose computer system, and the computer systems are connected to electronic communication media.

[0009] In one aspect of the invention, a fault tolerant system utilizing a plurality of general purpose computers equipped with PCI (peripheral components interconnection) comprises: a PCI monitoring card, connected to the general purpose computer by utilizing a PCI bus, for detecting faults by comparing the PCI bus signals of one of the general purpose computers with the PCI bus signals of the other general purpose computers; and network lines connecting the PCI monitoring card of one general purpose computer with the PCI monitoring cards of the other general purpose computers.

[0010] The PCI monitoring card is connected to the CPU(Central Processing Unit) of its computer by means of a the PCI bridge. The PCI monitoring card receives the address and data bus signals from its computer, and compares them with the address and data bus signals of the other computer. When they are different from each other, interrupt signals are generated. The PCI monitoring card transmits an interrupt signal to its computer and to the other computers.

[0011] The PCI monitoring card comprises: a FIFO( First In First Out ) memory for storing the received address and data bus signals by utilizing the PCI bus; compulsive stop logic for activating a stop signal to temporarily stop the PCI transaction when the capacity of the FIFO memory is stack full; communication ports for transmitting the address and data bus signals received from the FIFO memory to the other computers, or for receiving the address and data bus signals from the other computers; and a bus comparator for comparing the address and data bus signals of its computer with those of the other computers as respectively received from the FIFO memory and communication port, and for generating an interrupt signal when the signals are different from each other.

[0012] The FIFO memory, comprised of 32-bit clocked memories, stores the 32-bit address and data bus signals received from the PCI. When the FIFO memory is full, it generates a status signal in order to temporarily stop PCI bus transactions.

[0013] Communication ports, comprised of fiber channel communication ports, receive and transmit data from and to the other computers by utilizing fiber channels.

[0014] Communication ports, comprised of fast ethernet ports, receive and transmit data from and to the other computers by utilizing fast ethernet.

[0015] The bus comparator reports the interrupt signals to its computer and to the other computers through the PCI bus. The bus comparator comprises a dual 32-bit comparator for comparing the received 32-bit address and data bus signals.

[0016] In another aspect of the invention, a fault tolerant method utilizes the PCI (peripheral components interconnection) bus monitoring card, and comprises the steps of: receiving the address and data PCI bus signals from its computer; receiving the address and data PCI bus signals from the other computers through the network; comparing the address and data PCI bus signals of its computer with those of the other computers, and, when they are identical, comparing the next signals; generating an interrupt signal when the compared signals are different; transmitting an interrupt signal to its computer; and transmitting an interrupt signal to the other computers.

[0017] A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

[0018] FIG. 1 illustrates a schematic diagram of a fault detecting apparatus on the basis of CPU level;

[0019] FIG. 2 illustrates a schematic diagram of a fault detecting apparatus on the basis of input/output level;

[0020] FIG. 3 illustrates a schematic diagram of a fault detecting apparatus according to the present invention; and

[0021] FIG. 4 illustrates a schematic diagram of a PCI monitoring card structure.

[0022] FIG. 1 shows a schematic diagram of a fault detecting apparatus on the basis of CPU operation level. As illustrated, in order to detect fault on the basis of CPU operation level, two CPU boards (CPU board A, CPU board B) with identical structure are connected by utilizing the local buses 102. Each local bus 102 is connected to each CPU 100a, 100b, and carries data, address and control signals. CPU boards A and B have respective comparison logics 101a, 101bconnected to the local buses 102. The comparison logics 101a, 101bdetect fault by comparing the signals of the two local buses 102. When the signals of the two local buses 102 mismatch (that is, a fault occurs), the fault is reported to the CPU 100aor 100bby utilizing interrupt signals.

[0023] FIG. 2 shows a schematic diagram of a fault detecting apparatus on the basis of input/output bus level. As illustrated, in order to detect fault on the basis of the input/output level, CPU boards C and D with identical structure (including CPU's 200aand 200b, memories 201aand 201b, and local devices 202aand 202b) are connected by utilizing a dual input/output bus 205a, 205b. The CPU boards C and D have respective comparison logics 204a, 204bconnected to each input/output bus 205a, 205b. The comparison logics 204a, 204bdetect fault by comparing the dual input/output buses 205a, 205b. When the above-noted buses are different (that is, a fault occurs), the fault is reported to the CPU 200a, 200bthrough the input/output bridges 203a, 203b.

[0024] Fault detection systems utilizing the above-mentioned structure must have their own CPU boards or input/output buses. This increases the problem of designing or developing new systems, and causes the fault detection system to be more expensive than general purpose computer systems. Furthermore, adding fault detection logic to the CPU board causes the system to be complicated, thereby increasing the probability of fault or system failure.

[0025] FIG. 3 shows a schematic diagram of a fault detecting apparatus according to the present invention. As illustrated, the system includes: PCI bridges 304a, 304bconnected to CPUs 301a, 301bof the computers by utilizing the local buses 300a, 300b; PCI devices 306a, 306bconnected to the PCI bridges 304a, 304bby utilizing the PCI buses 305a, 305b; PCI monitoring cards 307a, 307bconnected to the PCI bridges 304a, 304bby utilizing the PCI buses 305a, 305b; and network lines 308a, 308binterconnecting the PCI monitoring cards 307a, 307bof the computers.

[0026] Each PCI monitoring card 307a, 307bis associated with a general purpose computer system, and they are connected by utilizing the network lines 308a, 308b.

[0027] The computers connected by utilizing the network lines 308a, 308bcheck each other's address and data bus via the PCI buses 305a, 305b, and transmit them to other computers. Therefore, a system fault is detected by concurrently comparing the system with other systems.

[0028] FIG. 4 shows an inner structure of the PCI monitoring cards 307a, 307bof FIG. 3. As illustrated, the PCI monitoring cards 307a, 307binclude: FIFO memories 400a, 400bwhich are 32-bit clocked, and which receive the address and data signals by utilizing the PCI buses 305a, 305bof their computers; compulsive stop logics 401a, 401bfor receiving status signals from the FIFO memories 400a, 400band transmitting stop signals to their computers; communication ports 403a, 403bfor transmitting the address and data signals received from the FIFO memories 400a, 400bto the other computers, and for receiving the address and data signals of the other computers; and dual 32-bit bus comparators 402a, 402bfor comparing the address and data signals received from the FIFO memories 400a, 400band the communication ports 403a, 403b, and for transmitting a mismatch signal to the other computers.

[0029] The FIFO memories 400a, 400bread AD[31:0] (that is, the address and data bus of the PCI bus 305a, 305b) and transmit them to the other computers by utilizing the fast networks of ports 403a, 403b, such as fiber channel or fast ethernet. The AD[31:0] of the FIFO memories 400a, 400bare concurrently transmitted to the bus comparators 402a, 402b, and are compared with the signals received from the other computers through the communication ports 403a, 403b.

[0030] When two compared signals do not match, the mismatched signals are reported to the CPU 301a, 301bof its computer as an interrupt signal. It is also transmitted to the other computer in order to facilitate fault detection.

[0031] When the FIFO memories 400a, 400bmemories are full, the transactions of the PCI bus 305a, 305bmust be stopped. Therefore, the full FIFO memories 400a, 400btransmit a status signal to the compulsive stop logics 410a, 401bso as to temporarily stop the transactions of the PCI buses 305a, 305b.

[0032] As previously mentioned, 32-bit clocked FIFO memories are utilized. The bus comparators 402a, 402bare arranged for dual 32-bit operation in order to compare the 32-bit bus signals of both computers. A fiber channel of 100 Mbps or a fast ethernet of 10BASE-T/100BASE-TX is utilized.

[0033] The operation of the present invention is now explained.

[0034] Each PCI monitoring card 307a, 307bis associated with a PCI bus 305a, 305bof the computer A, computer B. Each PCI monitoring card 307a, 307breceives and transmits the data of its computer and the other computer, and compares them concurrently. When the compared results are identical, which means that no fault is found, a next procedure is executed. When the compared results are different, the computer which detected the fault generates an interrupt signal and reports it to the other computer.

[0035] The operation of the present invention is explained in more detail with regard to computer A.

[0036] The signals from PCI bus 305a, as received through the AD[31:0] line, are written to the 32-bit clocked FIFO 400a. The AD[31:0] line is a multiplexed bus for the address and data of the PCI bus 305a. The capacity of the FIFO memory 400ais checked. When the capacity of the FIFO memory 400ais full, the FIFO memory 400atransmits a status signal to the compulsive stop logic 401a, and the compulsive stop logic 401ais activated to generate a stop signal STOP#. Therefore, the PCI transaction being executed or to be executed is temporarily stopped. After this, when the contents of the FIFO memory 400adecreases, the FIFO memory 400astarts storing data again.

[0037] The contents of the FIFO memory 400aare transmitted to the communication port 403athrough the AAD[31:0] line, the communication port 403abeing a fiber channel or a fast ethernet. The data leaving the NAAD[31:0] line of communication port 403aare transmitted to the NAAD[31:0] line of the other communication port 403b, thereby entering the dual 32-bit bus comparator 402bof computer B. The comparator 402bin computer B compares the entered data with the data received from the FIFO 400bof computer B.

[0038] Concurrently with the above operation, the data leaving the 32-bit clocked FIFO 400aare transmitted to the dual 32-bit bus comparator 402athrough the AAD[31:0] line 406a. The bus comparator 402ain computer A compares the data of the AAD[31:0] line with the data of the BAD[31:0] line received from computer B via communication ports 403a. When the compared data are identical, then the next data are compared. However, when the compared data are not identical, a mismatch signal is generated to activate the interrupt signal INTA# of computer A. Concurrently, the mismatch signal is transmitted to computer B so as to indicate that a fault is detected.

[0039] After receiving the interrupt signal computer A detects the fault and tries to determine the cause of the fault. Computer B also detects the fact that a fault has occurred in computer A, and tries to determine the cause of the fault. At this point, computers A and B stop all other operations and check the fault which has occurred.

[0040] The operation of the present invention will now be explained in more detail with regard to computer B.

[0041] The signals received through the AD[31:0] line are written to the 32-bit clocked FIFO 400b. The AD[31:0] line is a multiplexed bus of the address and data of the PCI bus 305b. The capacity of the FIFO memory 400bis checked. When the capacity of the FIFO memory 400bis full, the FIFO memory 400btransmits a status signal to the compulsive stop logic 401b, and the compulsive stop logic 401bis activated to generate a stop signal STOP#. Therefore, the PCI transactions being executed or to be executed are temporarily stopped. After this, when the contents of the FIFO memory 400bdecreases, the FIFO memory 400bstarts storing data again.

[0042] The contents of the FIFO memory 400bare transmitted to the communication port 403bthrough the line BAD[31:0], the communication port 403bbeing a fiber channel or a fast ethernet. The transmitted data leaving the NBAD[31:0] line of the communication port 403bare transmitted to the NBAD[31:0] line of the other communication port 403a, thereby entering the dual 32-bit bus comparator 402aof computer A. The comparator 402ain computer A compares the entered data with the data received from the FIFO 400aof computer A.

[0043] Concurrently with the above operation, the data leaving the 32-bit clocked FIFO 400bare transmitted to the dual 32-bit bus comparator 402bthrough the BAD[31:0] line 406b. The bus comparator 402bin computer B compares the data of the BAD[31:0] line with the data of the AAD[31:0] line received from computer A via communication port 403b. When the compared data are identical, then next data are compared. However, when the compared data are not identical, a mismatch signal is generated to activate the interrupt signal INTA# of computer B. Concurrently, the mismatch signal is transmitted to computer A so as to indicate that a fault is detected.

[0044] After receiving the interrupt signal, computer B detects the fault and tries to determine the cause of the fault. Computer A also detects the fact that a fault has occurred in computer B, and tries to determine the cause of the fault. At this point, computer A and B stop all other operations and check on the fault which has occurred.

[0045] It should be understood that the present invention is not limited to the particular embodiment disclosed herein as the best mode contemplated for carrying out the present invention, but rather that the present invention is not limited to the specific embodiments described in this specification except as defined in the appended claims.