Data processing system including different throughput access sources

Abstract: A data processing system includes a small throughput access source (12,13) and a large throughput access source (11) therein. Each of these access sources accesses a main storage unit (10) in a consecutive block access mode. The system further includes a detecting unit (14) and a selecting unit (15). The detecting unit (14) detects a conflict expected to occur. The selecting unit (15) responds to the detection by the detecting unit and momentarily stops the access by the small throughput access source (12,13) to give priority to the large throughput access source (11) for accessing the conflicting address of the main storage unit. The overall throughput of the system can thereby be maintained at a high level.

Description: The present invention relates to a data processing system including different throughput access sources, and more particularly to a control means, introduced in the system, for carrying out an access from a plurality of access sources having different throughputs to a main storage unit in a consecutive block access mode. Recently, along with an increase in scale of data handled in an information processing system, a scale of an access to the main storage unit in the system has also become large. In addition, there is a recent tendency for the main storage unit to be accessed by a variety of access sources, such as a vector processing unit, an extended storage unit and the like, other than usual access sources, such as a scalar processing unit, an input/output (I/O) processor, and the like. Under the circumstance mentioned above, a need has arisen for accessing the main storage unit by accessing addresses which specify each consecutive long addresses thereof. In relation to the consecutive long addresses, which hereinafter is referred to by the term "consecutive block access" which means that each memory area specified by consecutive addresses is divided into a plurality of blocks and the thus divided blocks are accessed sequentially. A usual working throughput therefor is hereinafter referred to as a "throughput of consecutive block access". In the above-mentioned data processing system including different throughput access sources, when a certain access source having large throughput starts accessing the main storage unit in the consecutive block access mode while another access source having small throughput has already started accessing the main storage unit in the consecutive block access mode, there is a high probability that a conflict in access will occur between both access sources at the same addresses of the main storage unit. In the case of such conflict, the access source having large throughput has to wait for a completion of the access to the main storage unit achieved by the other access source having small throughput, since, in the exemplified case, the former access source having large throughput starts the access after the access carried out by the latter access source having small throughput. This apparently reduces the total throughput of the related data processing system, and accordingly, it has long been hoped to improve the data processing efficiency. In the prior art, one proposal for improving data processing efficiency has been disclosed in a European Patent Application (Applicant FUJITSU LIMITED) with a publication number 0,215,621 (A2) published on March 25, 1987. According to the prior art, as depicted in Fig. 3 of the publication, the consecutive block accesses are performed intermittently so as to create nonaccess periods along the line of the consecutive block accesses. Thus, continual consecutive block accesses can cross the intermittent consecutive block accesses without conflict by passing through the aforesaid nonaccess period. The prior art, however, has a disadvantage that the aforesaid intermittent consecutive block accesses per se exhibit relatively low efficiency throughput. Accordingly, it is desirable to provide a data processing system including different throughput access sources, which system exhibits high efficiency throughput by not reducing the throughput of the access source having large throughput even if a conflict occurs with another access source having small throughput. According to the present invention, there is provided a data processing system including a main storage unit having interleaved banks, at least one small-throughput-access source, and at least one large-throughput-access source, each access source being operative to access said main storage unit in a consecutive block access mode, said system further comprising:- access request buffer means for temporarily storing access requests issued from said access sources; a detecting means for detecting, by monitoring the access requests stored in said access request buffer means, a conflict between one consecutive block access requested by a small-throughput-access source, and another consecutive block access requested by a large-throughput-access source; a selection unit, operative to pass therethrough either one of said access requests to said main storage unit selectively; and a selecting means, operative to control said selection unit, and when a conflict is detected by said detecting means, operative to stop the access request issued from a small-throughput-access source, so as to give priority of access of said main storage unit to a large-throughput-access source. In embodiments of the invention, a conflict expected to occur is detected first, which conflict is one occurring between a small throughput access source and a large throughput access source. Then, every time the aforesaid conflict is detected, the consecutive block access by the small throughput access source is momentarily stopped so as to prevent the conflict from occurring, so that the consecutive block access by the large throughput access source can be continued without any interruption. Thus, the large throughput can be maintained. In this case, the aforesaid momentary stoppage time of the small throughput access source is negligible compared to the delay time which would occur in the prior art to the large throughput access source due to an interruption by the small throughput access source when the conflict occurs. Reference is made, by way of example, to the accompanying drawings, wherein: Fig. 1 is a general view of a data processing system to which the present invention is applied; Figs. 2A and 2B depict access patterns for explaining a conflict between a large throughput block access and a small throughput block access; Fig. 3 illustrates a principle block diagram of a data processing system embodying the present invention; Fig. 4 depicts an access pattern for explaining the operation achieved in the system of Fig. 3; Fig. 5 illustrates a data processing system according to a first embodiment of the present invention; Fig. 6 is a circuit diagram of an example of the selecting circuit shown in Fig. 5; Fig. 7 is a circuit diagram of another example of the selecting circuit shown in Fig. 5; Fig. 8 illustrates an example of first and second holding means; Fig. 9 illustrates an example of an output stage of the busy check circuit; Fig. 10 illustrates a data processing system according to a second embodiment of the present invention; Fig. 11 is a circuit diagram of an example of the selecting circuit shown in Fig. 10; Fig. 12 is a circuit diagram of an example of the queue pointer monitoring circuit shown in Fig. 10; and Fig. 13 illustrates a data processing system according to a third embodiment of the present invention. Before describing the embodiments of the present invention, the conventional art and the disadvantages therein will be described with reference to the related figures. Figure 1 is a general view of a data processing system to which the present invention is applied. In Fig. 1, reference numeral 1 represents a main storage control unit (MCU) which controls a main storage unit (MSU) to which the present invention is mainly adopted. To be specific, the main storage control unit (MCU) 1 controls traffic of access requests issued from a variety of access sources, e.g., an extended storage control unit (ECU) 3, a vector processing unit (VU) 5, a scalar processing unit or units (SU) 6, an input/output processor (I/O) 7, and the like. The extended storage control unit (ECU) 3 controls the access to or from an extended storage unit (ESU) 4. The main storage unit (MSU) 2 usually assumes a structure of N (N ≧ 2) bank interleave. That is, (1) different banks can be accessed simultaneously by two or more access sources, and (2) the same bank can be accessed simultaneously only by one access source, and therefore another access source must wait for a while if it requires the bank, which is a characteristic of the N bank interleave. Further, the aforesaid consecutive block access relies greatly on the N bank interleave, and the aforesaid consecutive block access throughput also relies greatly thereon. Here, a problem arises in that there is a high probability of conflict between a consecutive block access generated by the access source of large throughput, e.g., the vector processing unit (VU) 5, and a consecutive block access generated by the access source of small throughput, e.g., the extended storage control unit (ECU) 3 in cooperation with the extended storage unit (ESU) 4. This will be clarified below with reference to the figures. Figures 2A and 2B depict access patterns for explaining a conflict between a large throughput block access and a small throughput block access. In each of Figs. 2A and 2B, the abscissa represents time while the ordinate represents an address, i.e., a bank number. Fig. 2A depicts an access pattern S (left upper stream) of a small throughput consecutive block access and an access pattern L (right lower stream) of a large throughput consecutive block access, where both consecutive block accesses S and L are carried out with high density. Fig. 2B depicts similar access patterns S and L to that of Fig. 2A, but, both consecutive block accesses S and L are carried out with low density. In Fig. 2A, the access patterns show that, during the access to the main storage unit by the access source having small throughput (refer to "S"), access to the main storage unit is simultaneously made by the access source having large throughput, and when the block access S to the address following the block number P is carried out, the block access L is also carried out to the same block number. In the above situation, a conflict occurs at the block numbers following the block number P, which areas are schematically illustrated with hatchings. In order to prevent the conflict from occurring, the access source of the access pattern L has to delay the start of the conflicting block address by a term α with respect to a flow of the current block access of small throughput S. Incidentally, reference character γ denotes a bank busy term, i.e., a term necessary for accessing each block. In Fig. 2B, even though the large throughput consecutive block access L is performed intermittently, the access L is to follow the small throughput consecutive block access S. Thus, the large throughput consecutive block access L can no longer get ahead of the small throughput consecutive block access S. As mentioned above, according to the conventional art, the consecutive block access generated by the access source having large throughput cannot get ahead of the consecutive block access generated by the access source having small throughput when a conflict occurs therebetween. Therefore a problem occurs in that the large throughput consecutive block access is reduced to an ability lower than its inherent high ability. In a typical and conventional data processing system, a long consecutive block access is not needed so frequently, and therefore, the above-mentioned problem does not matter. This is why a measure for overcoming the problem has not been previously discussed. However, in future systems, such a long consecutive block access will be needed frequently due to, for example, an employment of the vector processing unit (VU) together with the extended storage unit (ESU). Figure 3 illustrates a principle block diagram of a data processing system embodying the present invention. In Fig. 3, reference numeral 11 represents an access source (A) having large throughput, and 12 and 13 are access sources (B, C) having small throughputs. These access sources 11, 12 and 13 correspond to the access sources 3 through 7 shown in Fig. 1. Reference numeral 10 represents an N bank interleave main storage unit (MSU) which corresponds to the main storage unit (MSU) 2 shown in Fig. 1. The remaining part in Fig. 3 corresponds to the main storage control unit (MCU) 1 shown in Fig. 1, to which the present invention is mainly adopted. In general, according to the principle of the present invention, the aforesaid remaining part is comprised of a detecting means 14 for detecting a conflict between one consecutive block access requested by the access source 12 or 13 having small throughput and the other consecutive block access requested by the access source 11 having large throughput and a selecting means 15 for stopping, when the conflict is detected by the detecting means 14, an access request issued from the access source 12 or 13 having small throughput, whereby the selecting means 15 gives priority for accessing the main storage unit 10 to the access source 11 having large throughput. To be specific, in Fig. 3, the detecting means 14 and the selecting means 15 work with the aid of usual members, i.e., access request buffers 16, 17, and 18, and a selection unit 19. The detecting means 14 discriminates whether the conflict will occur or not by monitoring the access requests stored in the access request buffers 16, 17, and 18. If the detecting means 14 discriminates that the conflict will occur, the selecting means 15 commands the selection unit 19 to stop the access request, issued from the small throughput access sources 12 or 13, passing therethrough to the main storage unit 10, while the selecting means 15 commands the selection unit 19 to give priority to the access request, issued from the large throughput access source 11, for accessing the main storage unit 20. Figure 4 depicts an access pattern for explaining the operation achieved in the system of Fig. 3, which corresponds to the access patterns explained with reference to the previous Figs. 2A and 2B. Referring to both Figs. 4 and 3, the access requests issued from the access sources 11, 12, and 13 are momentarily stored in respective access request buffers 16, 17, and 18. These access requests are, on the one hand, monitored by the detecting means 14, and on the other hand, applied to the selection unit 19. The monitoring is performed to find whether the conflict is to occur. If the conflict occurs between, for example, the consecutive block access generated by the access source (B) 12 of small throughput and the consecutive block access generated by the access source (A) 11 of large throughput, the related conflict detection output is supplied to the selecting means 15. The selecting means 15 further analyzes the aforesaid conflict detection output, and if it confirms that the conflict will actually occur at the same bank number, it stops the access request generated by the access source (B) 12, while it allows the access request generated by the access source (A) 11 to pass through the selection unit 19, via a line L1. Thereby, the access source (A) 11 can access the main storage unit (MSU) 10. When the access source (A) 11 of large throughput finishes the access for the conflicting block, the conflict state with the access source (B) 12 will be removed. Therefore, the access source (B) 12 can restart the block access to the MSU 10. That is, in Fig. 4, the consecutive block access by the source (B) 12 is restarted after a suitable waiting period represented by the character β. Thereafter, the access source (B) 12 can continue its block access as before without any interruption. On the other hand, the access source (A) 11 can maintain its block access from beginning to end with its maximum access ability. It should be understood that the address used for the aforesaid detection of the conflict is expressed in terms of the bank number and the actual conflict is detected as a case where the access sources 11 and 12 specify the same bank. Figure 5 illustrates a data processing system according to a first embodiment of the present invention. In the first embodiment, the aforesaid access source having small throughput is exemplified by two access sources ("1" and "2") 20 and 21. Similarly, the aforesaid access source having large throughput is exemplified by two access sources ("3" and "4") 22 and 23. Reference numerals 24 represents an access source check circuit, 25 a busy check circuit, 26 a selecting circuit, and 27 a selection gate. Reference numerals 201, 211, 221, and 231 represent queue buffers which momentarily store therein respective access requests issued from the access sources ("1" through "4") 20 through 23. The access requests are supplied to the selection gate 27 via respective access ports 202, 212, 222 and 232. In general, according to the first embodiment, the aforesaid detecting means 14 is comprised of the busy check circuit 25 and the access source check circuit 24. The busy check circuit 25 is operative to check a busy state for each bank in the main storage unit (MSU) 10, and the access source check circuit 24 is operative to store therein identification information allotted to each access source ("1", "2") 20 and 21 having small throughput, which identification information is checked every time each access source ("3", "4") 22 or 23 having large throughput issues an access request. Thus, the selecting means, i.e., the selecting circuit 26, is operated according to both the output from the access source check circuit 24 and the output from the busy check circuit 25. The busy check circuit 25 and the access source check circuit 24 receive signals given from the access ports 202, 212, 222 and 232. Each of these signals from the access ports contain at least bank address information and the identification information. Thus, the busy check circuit 25 and the access source check circuit 24 produce a busy signal, if any, and a conflict signal, if any, respectively, which busy and conflict signals are supplied to the selecting means, i.e., the selecting circuit 26. Figure 6 is a circuit diagram of an example of the selecting circuit shown in Fig. 5. In general, according to the example, the selecting circuit 26 in Fig. 5 is comprised of logic gates (AND gates) corresponding to the access sources ("1" through "4"), respectively. Each logic gate corresponding to each access source ("3", "4") having large throughput receives at least a corresponding busy signal (BUSY 3, BUSY 4) and produces a GO signal (GO. 3, GO. 4) for starting access to the main storage unit 10, if the busy signal (BUSY 3, BUSY 4) indicates that no busy state exists ( BUSY 3 , BUSY 4 ). Each logic gate corresponding to each access source ("1", "2") having small throughput receives at least a corresponding busy signal (BUSY 1, BUSY 2) and the conflict signal (CONFLICT 3, CONFLICT 4) and produces a GO signal (GO. 1, GO. 2) for starting access to the main storage unit 10, if the busy signal indicates that no busy state exists ( BUSY 1 , BUSY 2 ) and the conflict signal indicates that no conflict state with the access source ("3", "4") having large throughput exists ( CONFLICT 3 , CONFLICT 4 ), however, if the busy state and/or the conflict state are found by the use of aforesaid busy and conflict signals, the related GO signal (GO. 1, GO. 2) is stopped thereby. Incidentally, signals represented by VALID 1, VALID 2, VALID 3 and VALID 4 are not essential to the present invention, but commonly used in the system for indicating a validity given, as a priority, to one of the access sources if identical access requests are issued, at the same time, for accessing the same bank. Regarding the logic gates shown in Fig. 6, as the selecting circuit 26, it is further necessary to stop the GO signal (GO. 1 or GO. 2) for a predetermined time, in order to restart the consecutive block access, after removing the related conflict. Hardware for realizing the above will be explained below. Figure 7 is a circuit diagram of another example of the selecting circuit shown in Fig. 5. In Fig. 7, each of the logic gates (AND gates) corresponding to the access source ("1", "2") having small throughput is provided with a timer means 28 which is operative to stop issuing the GO signals (GO. 1, GO. 2) for a predetermined time (β) after reception of the conflict signal (CONFLICT 3, CONFLICT 4) so that the related conflict state is removed within the predetermined time. Thereafter, the waiting access source ("1", "2"), can restart its own consecutive block access. The timer means 28 is specifically realized in the form of a shift register comprised of a plurality flip flops (FF's) connected in tandem. A first stage flip flop FF is set (S) by the signal CONFLICT 3 or CONFLICT 4 via an OR gate, as illustrated. Returning to Fig. 5, the busy check circuit 25 is comprised of first holding circuits allotted for respective banks in the main storage unit 10, and when a certain GO signal (GO. 1 through GO. 4), for starting access to the main storage unit 10, is issued from the selecting circuit 26, the corresponding flip flop is set. For example, if GO.1 signal is issued, the corresponding flip flop, specified by the address in the access port 202, is set, for a predetermined time after the issuance of the GO signal (GO. 1), which time (γ) is long enough for completing the related access to the main storage unit 10. Further, the access source check circuit 24 is comprised of second holding circuits allotted for respective banks in the main storage unit 10, and when a certain GO signal (GO. 1, GO. 2), for starting access to the main storage unit 10, is issued from the selecting circuit 26 in response to the access request from the access source ("1", "2") having small throughput, the related identification information is held in the corresponding holding circuit for a predetermined time after the issuance of the GO signal (GO. 1, GO. 2), which time (γ) is enough for completing the related access to the main storage unit 10. Figure 8 illustrates an example of first and second holding means. The first and second holding means can be formed separately, but in the example, both the first and second holding means are formed as one body for simplicity. The first holding means, comprising the busy check circuit 25, is realized by a plurality of flip flops 101. The second holding means, comprising the access source check circuit 24, is also realized by a plurality of flip flops 102. The first and second holding means further include commonly a shift register 103 and a decoder 104. The shift register 103 and the decoder 104 are used as a delay means for creating the term γ shown in Fig. 2A. It should be understood that, in the example, the main storage unit 10 is set up with four main storage areas. Each of the four main storage areas is composed of four modules. Each of the four modules is composed of thirty two banks. Therefore, these are 512 (4 x 4 x 32) banks in all. In the example of Fig. 8, only the first and second holding means, belonging to one of the 16 (4 x 4) modules, are illustrated for brevity. When the aforesaid bank address information is given from the access ports (202, 212, 222, 232), the corresponding one of the flip flops 101 is set by the output of a decoder 106 (SET 0 through SET 31). At the same time, if the bank address information is generated from the access source ("1", "2") having small throughput, the aforesaid identification information for discriminating the small throughput access source ("1" or "2") is also stored in the corresponding flip flop 102. At the same time, the aforesaid bank address information is supplied to the shift register 103 together with a valid bit (VALID 1 through VALID 4). After a certain delay time, the bank address information is supplied to the decoder 104. Thus the decoder 104 produces a corresponding one of the reset signals (RESET 0 through RESET 31), so that the previously set flip flops 101, 102 are reset thereby in order to accept a new bank address which will be given next. The busy check circuit 25 finally produces the aforesaid busy signals (BUSY 1 through BUSY 4) by the use of the aforesaid flip flops 101. Figure 9 illustrates an example of output stage of the busy check circuit. Reference characters BUSY 1 through BUSY 4 were already shown in Fig. 6. The output from the flip flops 101 (Fig. 8) are commonly applied to selection gates 105. When the access request is output from any one of the access ports (see 202, 212, 222, 232 in Fig. 5), the corresponding one of the selection gates 105 is opened to pass the busy signal therethrough (BUSY) if the busy state exists. In Fig. 9, reference characters ADRS 1 through ADRS 4 represent addresses sent from the access ports 202, 212, 222, 232, respectively, to select the corresponding holding circuit (flip flop 101). It is easily understood by a person skilled in the art that the output stage of the access source check circuit 24 can similarly be realized by the use of the circuit shown in Fig. 9 to produce the conflict signal (CONFLICT 3, CONFLICT 4). In this case, the flip flops 101 should be replaced by the flip flops 102. However, two selection gates among the four selection gates 105 of Fig. 9 is enough to produce the two conflict signals CONFLICT 3 and CONFLICT 4. Accordingly, two addresses ADRS 3 and ADRS 4 are needed therefor. Figure 10 illustrates a data processing system according to a second embodiment of the present invention. It should be noted that members identical to those explained before are indicated by the same reference numerals and characters (this also applies to later figures). In general, according to the second embodiment, the aforesaid detecting means 14 is comprised of the busy check circuit 25 and a queue pointer monitoring circuit 30. The point of the second embodiment is that the aforesaid conflict state can be found by watching a number of access requests accumulated in the queue buffers 221, 231 issued from the large throughput access sources "3", "4". The queue buffers are usually comprised of First In First Out (FIFO) memories. If the conflict between one consecutive block access and another consecutive block access takes place, it is very likely that the number of the access requests accumulated in the queue buffers 221, 231 will abnormally increase, since the throughput of the access sources "3" and "4" reduces due to the conflict. The busy check circuit 25 is operative to check a busy state for each bank in the main storage unit 10, as mentioned previously. The queue pointer monitoring circuit 30 is operative to monitor each usual queue pointer (223, 233) which cooperate with each queue buffer (221, 231) working, as mentioned previously, for momentarily storing therein the access request issued from the corresponding access source ("3", "4") having large throughput, and then operative to output an inhibit signal (INHIBIT 3, INHIBIT 4) when it monitors that the amount of the access requests, accumulated in the queue buffer (221, 231), reaches a predetermined upper level. Thus the selecting means 15 (Fig. 3), i.e., the selecting circuit 26 is operated according to both the output from the queue pointer monitoring circuit 30 and the output from the busy check circuit 25. It should be understood here that queue pointers similar to the queue pointers 223, 233 are also provided by each of the queue buffers 201 and 211, but are not shown in Fig. 10, since these queue pointers are not used for the present invention. As in the first embodiment (Fig. 5), the busy check circuit 25 receives signals given from the access ports 202, 212, 222, and 232, and each of these signals from the access ports contain at least bank address information and identification information allotted to each said access source. Thus the busy check circuit 25 and the queue pointer monitoring circuit 30 produce the busy signal, if any, and the inhibit signal, if any, respectively, which busy and inhibit signals are supplied to the selecting means, i.e., the selecting circuit 26. Figure 11 is a circuit diagram of an example of the selecting circuit shown in Fig. 10. The construction of the selecting circuit 26 is the same as that shown in Fig. 6. The difference between the selecting circuits 26 of Fig. 6 and Fig. 11 is that the circuit 26 of Fig. 11 receives as an input the signals INHIBIT 3 and INHIBIT 4, instead of CONFLICT 3, CONFLICT 4, as in Fig. 6. Each logic gate corresponding to each said access source ("1", "2") having small throughput receives at least a corresponding busy signal (BUSY 1, BUSY 2) and the inhibit signal (INHIBIT 3, INHIBIT 4) and produces the aforesaid GO signal (GO. 1, GO. 2) for starting access to the main storage unit 10, if the busy signal indicates that no said busy state exists ( BUSY 1 , BUSY 2 ) and the inhibit signal indicates that no conflict state with the access source ("3", "4") having large throughput exists ( INHIBIT 3 , INHIBIT 4 ), however, if the busy state and/or the conflict state (inhibit state) are found by the use of the aforesaid busy and inhibit signals, the related GO signal is stopped thereby. The meaning of the reference "VALID" has already been explained. Regarding the logic gates shown in Fig. 11, for the selecting circuit 26, as mentioned previously in reference to the first embodiment, it is further necessary to stop the GO signal (GO. 1 or GO. 2) for a predetermined term, in order to restart the consecutive block access, after removing the related conflict. Hardware for realizing the above is the same as that shown in Fig. 7. In Fig. 7, the signals INHIBIT 3, INHIBIT 4 in parentheses should be used for the second embodiment, instead of the signals CONFLICT 3, CONFLICT 4. The busy check circuit 25 is comprised of holding circuits (refer to flip flops 101 in Fig. 8) allotted for respective banks in the main storage unit 10, and when a certain GO signal, GO. 1 through GO. 4 for starting access to the main storage unit 10, is issued from the selecting circuit 26, the corresponding flip flop is set. For example, if GO. 1 signal is issued, the corresponding flip flop, specified by the address in the access port 202, is set, for a predetermined time after the issuance of the GO signal (GO. 1), which time is long enough for completing the related access to the main storage unit 10. Figure 12 is a circuit diagram of an example of the queue pointer monitoring circuit shown in Fig. 10. The queue pointer monitoring circuit 30 is comprised of a subtraction circuit 31 receiving the first output and the second output from a write counter 32 and a read counter 33, respectively, which two counters 32, 33 form the aforesaid queue pointers 223 (233). The subtraction circuit 31 produces the inhibit signal INHIBIT 3 (INHIBIT 4) every time the resultant subtraction value reaches the predetermined upper level, i.e., a threshold level given in advance to the subtraction circuit 31. Figure 13 illustrates a data processing system according to a third embodiment of the present invention The point of the third embodiment is that the aforesaid conflict state can be found by watching a number of cases in each of which the large throughput access source has to wait for a relatively long time to start its consecutive block access. In the third embodiment, the detecting means is comprised of a busy check circuit 25 common to the first and second embodiment, and a counting means 40. As mentioned previously, the busy check circuit 25 is operative to check a busy state for each bank in the main storage unit. The third embodiment features the counting means 40 which is comprised of a first counting circuit 41 (42) and a second counting circuit 43 (44). The first counting circuit 41 (42) measures a time interval between each of two consecutive timings at each of which the access request is issued from the access source "3" ("4") having large throughput and produces a time-out signal every time the time interval exceeds a predetermined upper level. The second counting circuit 43 (44) counts a number of time-out signals, given from the first counting circuit 41 (42) per unit of time and produces an inhibit signal INHIBIT 3 (INHIBIT 4) when a number of the time-out signals exceeds a predetermined upper level. Thus the selecting means, i.e., the selecting circuit 26, is operated according to both the output from the counting means 40, especially the second counting circuit 43 (44) and the output from the busy check circuit 25. As in the first and second embodiments, the busy check circuit 26 receives signals given from the access ports 202, 212, 222 and 232 provided for respective access sources "1" through "4". Each of these signals from the access ports contain at least bank address information and identification information allotted to each said access source. Thus the busy check circuit 25, and the counting means 40 produces the busy signal, if any, and inhibit signal (INHIBIT), if any, respectively, which busy and inhibit signals are supplied to the selecting circuit 26. The selecting means, i.e., the selecting circuit 26 is substantially the same in a construction as that shown in Fig. 11. The selecting circuit 26, i.e., logic gates (AND gates) should cooperate with the aforesaid timer means, as explained with reference to Fig. 7. The busy check circuit 25 can be comprised of the aforesaid holding circuits (refer to flip flops 101 shown in Fig. 8). The function of the holding circuits has already been explained with reference to the related Fig. 8. The first counting circuit 41 (42) measures the time interval by receiving subsequent GO signals GO. 3 (GO. 4), each of which is output from the selecting means, i.e., the selecting circuit 26, for starting access to the main storage unit 10 in response to the access request issued by the access source "3" ("4") having large throughput. The second counting circuit 43 (44) is provided with a reset timer 45 (46) which periodically clears the content of the second counting circuit 43 (44) at constant intervals. The constant interval is determined to be not shorter than several times a delay time plus the bank busy time, i.e., one block access time (refer to γ in Fig. 2A), which delay time is a minimum time required for removing the conflict (refer to α in Fig. 2A). In Fig. 13, reference numerals 47 and 48 represent output buffers to connect with the logic gates in the selecting circuit 26. As explained above in detail, the present invention can prevent the data processing system from being reduced in throughput, even if a conflict is expected to occur between the small throughput access source and the large throughput accessing source by removing the conflict and giving priority to the large throughput access source for accessing the main storage unit.

Claims: A data processing system including a main storage unit (10) having interleaved banks, at least one small-throughput-access source (12, 13, 20, 21), and at least one large-throughput-access source (11, 22, 23), each access source being operative to access said main storage unit (10) in a consecutive block access mode, characterised in that said system further comprising:- access request buffer means (16, 17, 18) for temporarily storing access requests issued from said access sources (11, 12, 13, 20, 21, 22, 23); a detecting means (14) for detecting, by monitoring the access requests stored in said access request buffer means (16, 17, 18), a conflict between one consecutive block access requested by a small-throughput-access source (12, 13, 20, 21), and another consecutive block access requested by a large-throughput-access source (11, 22, 23); a selection unit (19, 27), operative to pass therethrough either one of said access requests to said main storage unit (10) selectively; and a selecting means (15, 26), operative to control said selection unit (19, 27), and when a conflict is detected by said detecting means (14), operative to stop the access request issued from a small-throughput-access source (12, 13, 20, 21), so as to give priority of access of said main storage unit (10) to a large-throughput-access source (11, 22, 23). A data processing system as set forth in claim 1, wherein said access request buffer means (16, 17, 18) comprises access request buffers (201, 211, 221, 231) and access ports (202, 212, 222, 232) provided respectively for each of said access sources and located between the access sources and the main storage unit (10); and said detecting means (14) comprises a busy check circuit (25) and an access source check circuit (24); and wherein: said busy check circuit (25) is operative to check a busy state for each bank in said main storage unit (10), and said access source check circuit (24) is operative to store therein identification information allotted to each small-throughput-access source (20, 21), which identification information is checked every time a large-throughput-access source (22, 23) issues an access request when it is found that the access request is not allowed due to said busy state checked in said busy check circuit (25); the busy check circuit (25) and the access source check circuit (24) are operative to produce a busy signal or a conflict signal, respectively, by using signals from the access ports (202, 212, 222, 232) containing at least bank address information and said identification information; said selecting means (26) is responsive to the busy and conflict signals for producing a GO signal for enabling access of said main storage unit (10) by one of said access sources (20, 21, 22, 23), said GO signal corresponding to a large-throughput-access source if no busy state exists, and corresponding to a small-throughput-access source if no busy state exists and no conflict state exists with a large-throughput-access source; said busy check circuit (25) comprising first holding circuits (101) allotted for respective banks in said main storage unit (10), arranged such that when a certain GO signal (GO.1 to GO.4) is issued from said selecting means (26), the related busy signal is held in the corresponding holding circuit for a predetermined time after the issuance of the GO signal, which time is long enough for completing the related access to the main storage unit; and said access source check circuit (24) comprising second holding circuits (102) allotted for respective banks in said main storage unit (10), arranged such that when a certain GO signal (GO.1 to GO.4) is issued from said selecting means (26) in response to the access request from a small-throughput-access source (20, 21), the related identification information is held in the corresponding holding circuit (102) for a predetermined time after the issuance of the GO signal, which time is long enough for completing the related access to the main storage unit. A data processing system as set forth in claim 2, wherein said selecting means (26) comprises a logic gate corresponding to each access source (20, 21, 22, 23), respectively; wherein each logic gate corresponding to a large-throughput-access source (22, 23) is responsive to at least a corresponding busy signal (BUSY3, BUSY4) to produce a corresponding GO signal (GO.3, GO.4) if no busy state exists; each logic gate corresponding to a small-throughput-access source (20, 21) is responsive to at least a corresponding busy signal (BUSY1, BUSY2) and said conflict signal (CONFLICT3, CONFLICT4) to produce a corresponding GO signal (GO.1, GO.2) if no busy state exists and no conflict state with an large-throughput-access source exists, and to stop the related GO signal if the busy state and/or the conflict state exists. A data processing system as set forth in claim 3, wherein each logic gate corresponding to a small-throughput-access source (20, 21) is provided with a timer means (28) which is operative to stop issuing said GO signal (GO.1 to GO.4) for a predetermined time after receipt of said conflict signal (CONFLICT3, CONFLICT4), so that the related conflict state is removed within the predetermined time. A data processing system as set forth in claim 1, wherein a respective queue buffer (201, 211, 221, 231) is provided for each of said access sources (20, 21, 22, 23) and is operative to temporarily store access requests from the same, and wherein said detecting means (14) comprises a busy check circuit (25) and a queue pointer monitoring circuit (30); wherein: said busy check circuit (25) is operative to produce a busy signal by checking a busy state for each bank in said main storage unit (10), based on signals given from respective access ports (202, 212, 222, 232) provided for each of said access sources (20, 21, 22, 23) and located between these access sources and said main storage unit (10), each of said signals from the access ports containing at least bank address information and an identification information allotted to the respective access source; said queue pointer monitoring circuit (30) is operative to monitor queue pointers (223, 233) which co-operate with each queue buffer provided for a large-throughput-access source (22, 23) and to output an inhibit signal (INHIBIT3, INHIBIT4) indicating a conflict state, when a predetermined number of access requests in the queue buffer is reached; and said selecting means (26) is responsive to the busy and inhibit signals to produce a GO signal for enabling access of said main storage unit (10) by one of said access sources (20, 21, 22, 23), said GO signal corresponding to a large-throughput-access source if no busy state exists, and corresponding to a small-throughput-access source if no busy state exists and no conflict state exists with a large-throughput-access source; and said busy check circuit (25) comprises holding circuits allotted for respective banks in said main storage unit (10), and when a certain GO signal is issued from said selecting means, the related busy signal is held in the corresponding holding circuit for a predetermined time after the issuance of the GO signal, which time is long enough for completing the related access to the main storage unit. A data processing system as set forth in claim 5, wherein said selecting means (26) comprises a logic gate corresponding to each access source (20, 21, 22, 23), respectively; wherein: each logic gate corresponding to a large-throughput-access source (22, 23) is responsive to at least a corresponding said busy signal (BUSY3, BUSY4) to produce a corresponding GO signal (GO.3, GO.4), if no busy state exists; each logic gate corresponding to a small-throughput-access source (20, 21) is responsive to at least a corresponding said busy signal (BUSY1, BUSY2) and said inhibit signal (INHIBIT3, INHIBIT4) to produce a corresponding GO signal (GO.1, GO.2) if no busy state exists with a large-throughput-access source, and to stop the related GO signal if the busy state and/or the conflict state exists. A data processing system as set forth in claim 6, wherein each logic gate corresponding to a small-throughput-access source (20, 21) is provided with a timer means which is operative to stop issuing said GO signal for a predetermined time after reception of said inhibit signal, so that the related conflict state is removed within the predetermined time. A data processing system as set forth in any one of claims 5 to 7, wherein said queue pointer monitoring circuit comprises a subtraction circuit (31) receiving the first output and the second output from a write counter (32) and a read counter (33), respectively, which two counters form a said queue pointer (223, 233); said subtraction circuit (31) being operative to produce said inhibit signal (INHIBIT3, INHIBIT4) every time the resultant subtraction value reaches said predetermined number. A data processing system as set forth in claim 1, wherein said detecting means (14) comprises a busy check circuit (25) and a counting means (40); and wherein: said busy check circuit (25) is operative to produce a busy signal by checking a busy state for each bank in said main storage unit (10), based on signals given from respective access ports (202, 212, 222, 232) provided for the access sources (20, 21, 22, 23) and located between these access sources and said main storage unit (10), each of said signals from the access ports containing at least bank address information and identification information allotted to each access source; said counting means (40) comprises a first counting circuit (41, 42) and a second counting circuit (43, 44), provided respectively for each large-throughput-access source (22, 23), the first counting circuit measuring a time interval between successive timings at which an access request is issued from a large-throughput-access source (22, 23) and produces a time-out signal every time the time interval exceeds a predetermined upper level, and said second counting circuit (43, 33) counting a number of the time-out signals, from said first counting circuit (41, 42) per unit of time and produces an inhibit signal (INHIBIT3, INHIBIT4), indicating a conflict state, when a predetermined number of time-out signals is exceeded; said selecting means (26) being responsive to the busy and inhibit signals for producing a GO signal for enabling access of said main storage unit (10) by one of said access sources (20, 21, 22, 23), said GO signal corresponding to a large-throughput-access source if no busy state exists, and corresponding to a small-throughput-access source if no busy state exists and no conflict state exists with a large-throughput-access source; wherein said busy check circuit (25) comprises holding circuits (101, 102) allotted for respective banks in said main storage unit (10), arranged such that when a certain GO signal is issued from said selecting means (26), the related busy signal is held in the corresponding holding circuit for a predetermined time after the issuance of the GO signal, which time is long enough for completing the related access to the main storage unit. A data processing system as set forth in claim 9, wherein said selecting means (26) comprises a logic gate corresponding to each access source (20, 21, 22, 23), respectively; each logic gate corresponding to a large-throughput-access source (22, 23) receives at least a corresponding busy signal (BUSY3, BUSY4) and produces a corresponding GO signal (GO.3, GO.4), if the busy signal indicates that no busy state exists; and each logic gate corresponding to a small-throughput-access source (20, 21) receives at least a corresponding busy signal (BUSY1, BUSY2) and said inhibit signal (INHIBIT3, INHIBIT4) and produces a corresponding GO signal (GO.1, GO.2) no busy state exists and no conflict state exists with large-throughput-access source (22, 23) but stops the related GO signal if the busy state and/or the conflict state exists. A data processing system as set forth in claim 10, wherein each logic gate corresponding to a small-throughput-access source (20, 21) is provided with a timer means (28) which is operative to stop issuing said GO signal (GO:1, GO.2) for a predetermined time after receipt of said inhibit signal (INHIBIT3, INHIBIT4), so that the related conflict state is removed within the predetermined time. A data processing system as set forth in claim 9, 10, or 11, wherein said first counting circuit (41, 42) measures the time interval by receiving successive GO signals (GO.3, GO.4), each of which is output from said selecting means (26) in response to a said access request issued by a large-throughput-access source (22, 23). A data processing system as set forth in any one of claims 9 to 12, wherein said second counting circuit (43, 44) is provided with a reset timer (45, 46) which periodically clears the content of the second counting circuit at constant intervals. A data processing system as set forth in claim 13, wherein said constant interval is determined to be not shorter than several times a delay time plus a bank busy time, i.e. one block access time, which delay time is a minimum time required for removing the conflict.

Inventors: KOREKATA KENJI FUJITSU DAI NAK, UCHIDA NOBUO, KOREKATA, KENJI FUJITSU DAI 14 NAKAHARA-RYO,1676-1, UCHIDA, NOBUO
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1989
Main classification: G06F13
IPC codes: G06F15, G06F12, G06F13