Abstract: A hierarchical bus structure is disclosed in which clusters of processors are arranged and interconnected within a hierarchy to facilitate processor communications via shared memories. The bus structure is well suited for voice processing applications in which clusters of embedded processors process voice streams in parallel, although the architecture is not so limited. Also disclosed is a memory access protocol in which the address and data portions of shared-memory access operations are performed as separate bus transactions that are separated in time, such that multiple concurrent memory access operations from different processors may be interleaved over a shared bus.

Abstract: Disclosed is a multiprocessor apparatus including a co-processor provided in common to a plurality of processors and including a plurality of resources and an arbitration circuit that arbitrates contention among the processors with respect to use of a resource in the co-processor by the processors through a co-processor bus, which is a tightly coupled bus, for each resource or each resource hierarchy according to instructions issued from the processors to the co-processor. Under control by the arbitration circuit, simultaneous use of a plurality of resources on a same hierarchy or different hierarchies in the co-processor by the processors through the tightly coupled bus is allowed.

Abstract: The present invention includes a network having a plurality of communication buses, at least two of the plurality of buses utilizing different communication bus protocols; a plurality of computer devices, at least one of the plurality of computer devices coupled to at least one of the plurality of communication buses and containing computer device software having an architecture including bus communication software for communicating with at least one of the plurality of communication buses; and an abstraction layer in communication with the bus communication software and capable of abstracting messages from the communication bus protocols, the plurality of computer devices including at least one gateway computer device coupled to multiple of the plurality of communication buses and containing computer device software having an architecture further including a gateway in communication with the abstraction layer and capable of routing the abstracted messages between computer devices coupled to the multiple comm

Abstract: A scalable, two-stage rotating priority arbiter with re-circulation and bounded latency for use in multi-threaded, multi-processing devices. An apparatus implementing the two-stage arbiter includes a plurality of masters configured in a plurality of clusters, a plurality of targets, and an chassis interconnect that may be controlled to selectively connects a given master to a given target. The chassis interconnect includes multiple sets of bus lines connected between the plurality of clusters and the plurality of targets forming a cross-bar interconnect, including sets of bus lines corresponding to a command bus. A two-stage arbitration scheme is employed to arbitrate access to the command bus. The first arbitration stage is used to arbitrate between target requests issued by masters in a given cluster. The second arbitration stage is used to arbitrate between winning first-stage target requests. One embodiment of the arbitration scheme employs a rotating priority arbitration scheme at the first stage.

Abstract: A queued interface device configured to communicate with a peripheral includes a first interface configured to receive and store a first set of peripheral requests from a first core, a second interface configured to receive and store a second set of peripheral requests from a second core, and an arbitrator coupled to the first interface and the second interface. The arbitrator, which may include multiple sets of registers to store the peripheral requests, is configured to selectively send the first set of peripheral requests and the second set of peripheral requests to the peripheral. The peripheral simultaneously appears as a dedicated peripheral for both the first and second cores.

Abstract: A data packet routing mechanism including a plurality of clients for issuing read requests to a host device, the read requests each including a TAG field for identifying which of the plurality of clients issued a particular read request, wherein a completion response corresponding to the particular read request, including the TAG field, is issued from the host to the client that sent the read request, the plurality of clients being organized into M groups, each group including a predetermined number of clients; a first level routing device having an input for receiving completion responses from the host and a plurality of outputs for transmitting completion responses; and a plurality of second level routing devices, each being coupled to the plurality of clients in one of the M groups, and having an input for receiving completion responses from the first level routing device and a plurality of outputs, each output for transmitting completion responses to one of the plurality of clients in the group.

Abstract: A method, a system and a computer programmable product have been provided for arbitrating bus cycles among a plurality of device nodes. Requests for bus grant are received from the device nodes. Each request includes values of one or more arbitration parameters. The requests grouped at a first stage, with two requests in each group. A comparison is performed in each group, based on the values of the one or more parameters. Further, winners from each comparison are forwarded to a next stage. Subsequently, comparisons are performed over one or more stages to select a winner of the bus grant.

Abstract: A hierarchical bus structure is disclosed in which clusters of processors are arranged and interconnected within a hierarchy to facilitate processor communications via shared memories. The bus structure is well suited for voice processing applications in which clusters of embedded processors process voice streams in parallel, although the architecture is not so limited. Also disclosed is a memory access protocol in which the address and data portions of shared-memory access operations are performed as separate bus transactions that are separated in time, such that multiple concurrent memory access operations from different processors may be interleaved over a shared bus.

Abstract: A distributed radar data processing system for generating data to be supplied to air traffic control by processing radar data obtained from a radar device, comprises a plurality of data buses provided in accordance with types of flowing data, a plurality of applications which is distributed and allocated to each of a plurality of hierarchical layers separated by the plurality of data buses, and connected to two of the data buses configuring a particular layer to realize a predetermined function, and a distribution and integration interface for controlling a connection between the plurality of applications.

Abstract: Method and system for arbitrating between plural arbitration requests is provided. The system includes a plurality of first stage arbiters that receive plural arbitration requests and a signal that indicates a previously granted request, wherein the first stage arbiters assert a high priority request signal if a high priority request is pending and a low priority request signal is asserted, if a low priority request is pending; a second stage arbiter that arbitrates between high priority requests, when high priority requests are pending; wherein if a high priority request is not pending, then a low priority request is granted; and a data handler module that operates in parallel with the second stage arbiter to immediately move data associated with a request that is granted at any given time.

Abstract: Methods and apparatus for supporting programmable burst management schemes on pipelined buses. The apparatus includes a plurality of bus masters (masters), configured in a plurality of clusters, and a plurality of target sub-groups. Each target sub-group includes one or more shared resource targets. A scalable chassis infrastructure is used to interconnect the targets with the clusters using a crossbar interconnect configuration including pipelined command, and data buses. The interconnect includes sub-group multiplexers for each sub-group and sub-group selection multiplexers coupled to each cluster. A two-stage arbiter, operatively coupled to the targets, sub-group multiplexers, and sub-group selection multiplexers, is employed to arbitrate transaction requests issued from the masters to the targets and manage transactions. The two-stage arbiter includes a provision for supporting programmable burst management, wherein selected sub-groups can be tuned for handling short or long burst traffic.

Abstract: A method for intervaled memory transfer access provides periodic authorization signals to a memory access controller. The method cycles between: 1) inhibiting the memory access controller from writing data to a memory until the memory access controller receives a periodic authorization signal to cause the memory access controller to remove the inhibition and write a predetermined amount of data to the memory through a data bus, and 2) releasing the data bus following writing of the predetermined amount of data to the memory by inhibiting the memory access controller from writing further data.

Abstract: A method for arbitrating access to a data bus among subscribers or bus devices (Tn 1,Tn 2, . . . ), wherein the bus devices are coupled by at least one arbitration ring (12; 38, 40, 42, 44, 46, 48). The method comprises the following steps: a) requesting access by a first bus device; b) checking whether a first signal, which indicates that the arbitration ring is enabled, is present at an input (16) of the first bus device; c) if the first signal is present, outputting (18) a second signal by the first bus device; d) checking whether, at the end of a predetermined time period, the first signal is still present at the input (16) of the first bus device; and e) if the first signal is still present at the end of the predetermined time period, accessing the data bus by the first bus device.

Abstract: The information processing device comprises first and second master circuits and an arbiter for arbitrating access rights to a bus to which the master circuits are connected. The arbiter has storage units retaining information representing priorities of the access rights, and an arbitration control logical unit for arbitrating the access rights of the master circuits based on the information. When the priority of the first master circuit is higher than the priority of the second master circuit and there is no access request from the first master circuit but there is an access request from the second master circuit, the arbitration control logical unit permits access of the second master circuit, and the storage units lower the priority of the second master circuit without changing the priority of the first master circuit.

Abstract: Round robin arbitration system includes a first round robin arbitration module and a second round robin arbitration module. The first round robin arbitration module has a first bit width. It is configured to partition a plurality of requests into a plurality of blocks of requests, to select a block having one or more active requests using round robin arbitration, and to generate a first index corresponding to the selected block. The second round robin arbitration module has a second bit width. It is configured to store each request of the selected block, to select each active request of the selected block using round robin arbitration, to generate a second index corresponding to the selected active request, and to generate a first signal for synchronizing operation of the first and second modules. The round robin arbitration system has a bit width that is a product of the first and second bit width.

Abstract: A fair hierarchical arbiter comprises a number of arbitration mechanisms, each arbitration mechanism forwarding winning requests from requestors in round robin order by requestor. In addition to the winning requests, each arbitration mechanism forwards valid request bits, the valid request bits providing information about which requestor originated a current winning request, and, in some embodiments, about how many separate requesters are arbitrated by that particular arbitration mechanism. The fair hierarchical arbiter outputs requests from the total set of separate requestors in a round robin order.

Abstract: A scalable, two-stage round-robin arbiter with re-circulation and bounded latency for use in multi-threaded, multi-processing devices. An apparatus implementing the two-stage arbiter includes a plurality of masters configured in a plurality of clusters, a plurality of targets, and an chassis interconnect that may be controlled to selectively connects a given master to a given target. The chassis interconnect includes multiple sets of bus lines connected between the plurality of clusters and the plurality of targets forming a cross-bar interconnect, including sets of bus lines corresponding to a command bus. A two-stage arbitration scheme is employed to arbitrate access to the command bus. The first arbitration stage is used to arbitrate between command requests issued by masters in a given cluster. The second arbitration stage is used to arbitrate between winning first stage command requests. One embodiment of the arbitration scheme employs re-circulation of second stage losers.

Abstract: A computer system having a hierarchical bus structure that allows decoupling of a local bus from a global bus thereof. Decoupling of the local bus is achieved through use of an asynchronous system bus adapter which includes a local bus adapter for handling transactions, initiated by a system device coupled to the global bus, that require access to a local device coupled to the local bus and a global bus adapter for handling transactions, initiated by a local device coupled to the local bus, that require access to a system device coupled to the system bus. The local bus adapter is further configured to issue signals which prevent the global bus adapter from handling transactions initiated by local devices coupled to the local bus while transactions initiated by system devices coupled to the global bus are on-going.

Abstract: A multiprocessor system having a plurality of processor elements each of which obtains right to use bus of a first or second shared bus in response to a transfer request for control system data or input/output data and as a master, conducts multiplex-transfer or burst-transfer, in which the processor element outputs a bus request signal for the first shared bus in response to a transfer request for the control system data and as a master, transfers and outputs a selection signal, a control signal and an address signal of a transfer destination and the control system data in one cycle in response to application of a bus grant signal, and is selected as a slave based on the selection signal through the first shared bus to receive input of the control system data and process the data based on the control signal and the address signal.

Abstract: The present invention is to provide a bus arbitration apparatus and a bus arbitration method not reducing data transfer capability as a whole and preventing a loss of transferred data. It performs the arbitration with priority in response to properties of bus masters. It sequentially arbitrates a first hierarchy bus master of which requests are urgent, a second hierarchy bus master that requests data processing in real time, and a third hierarchy bus master that is neither a first hierarchy bus master nor a second hierarchy bus master sequentially.

Abstract: A statistic method for arbitration is provided, implementing in an arbitration system comprising a bus, a main controller connected to the bus, and a plurality of peripheral devices able to be accessed by the main controller through the bus. The statistic method for arbitration is in response to various conditions where a bus is shared by peripheral devices, characterized in that a host at arbitration dynamically modulates the peripheral devices' access through the bus by utilizing an attenuation function to perform operation on a preceding cycle and a statistic value representing the use of the bus by the peripheral devices in response to the peripheral devices' access through the bus.

Abstract: A method of communicating between an initial device and a target device connected by a plurality of intermediate segments in a distributed arbitration system is provided. The method includes establishing an arbitration timer for a communication request by the initial device. Furthermore, use of each of the intermediate segments is arbitrated based on the arbitration timer.

Abstract: A binary-tree-based arbitration system and methodology with attributes that approximate a Generalized Processor Sharing (GPS) scheme for rendering fairer service grants in an environment having a plurality of competing entities. Arbitration based on probabilistic control of arbiter nodes' behavior is set forth for alleviating the inherent unfairness of a binary tree arbiter (BTA). In one implementation, BTA flag direction probabilities are computed based on composite weighted functions that assign relative weights or priorities to such factors as queue sizes, queue ages, and service class parameters. Within this general framework, techniques for desynchronizing a binary tree's root node, shuffling techniques for mapping incoming service requests to the BTA's inputs, and multi-level embedded trees are described.

Abstract: Round robin arbitration system includes a first round robin arbitration module and a second round robin arbitration module. The first round robin arbitration module has a first bit width. It is configured to partition a plurality of requests into a plurality of blocks of requests, to select a block having one or more active requests using round robin arbitration, and to generate a first index corresponding to the selected block. The second round robin arbitration module has a second bit width. It is configured to store each request of the selected block, to select each active request of the selected block using round robin arbitration, to generate a second index corresponding to the selected active request, and to generate a first signal for synchronizing operation of the first and second modules. The round robin arbitration system has a bit width that is a product of the first and second bit widths.

Abstract: A method and system for managing distributed arbitration for multi-cycle data transfer requests provides improved performance in a processing system. A multi-cycle request indicator is provided to a slice arbiter and if a multi-cycle request is present, only one slice is granted its associated bus. The method further blocks any requests from other requesting slices having a lower latency than the first slice until the latency difference between the other requesting slices and the longest latency slice added to a predetermined cycle counter value has expired. The method also blocks further requests from the first slice until the predetermined cycle counter value has elapsed and blocks requests from slices having a higher latency than the first slice until the predetermined cycle counter value less the difference in latencies for the first slice and for the higher latency slice has elapsed.

Abstract: An object of the present invention is to provide a multi-function peripheral which is easy for a user to operate. To achieve the object, according to the present invention, there is provided a peripheral connected to an information processing apparatus, which inputs and analyzes a job script constituted of packet data from the information processing apparatus, and subsequently generates an appropriate job file in accordance with the content of the job script.

Abstract: A computer system including a first repeater and a second repeater that is coupled to the first repeater. The computer system also includes a third repeater that is coupled to the first repeater. The first repeater contains a first arbiter that arbitrates transactions between the first repeater and the second repeater and also arbitrates transactions between the first repeater and the third repeater. The second repeater receives transactions from the first repeater and contains a second arbiter that predicts receipt of transactions from the first repeater to the second repeater.

Abstract: Circuits and associated methods for operation thereof for gathering real-time statistical information regarding operation of the arbiter circuit in a particular system application. The real-time statistical information so gathered is useful for off-line analysis by a system designer for determining optimal configuration and parameter values associated with operation of a particular arbiter in a specific system application. In a first exemplary preferred embodiment, a timer circuit associated with the arbiter measures a predetermined period of time during which statistical data is to be gathered. Counter circuits associated with the arbiter count the number of occurrences of events of interest to the designer during the time period measured by the timer circuit. Each counter circuit preferably senses and counts a particular event of interest to the designer.

Abstract: A computer system including a first repeater; a second repeater coupled to the first repeater; and a third repeater coupled to the first repeater. The second repeater is also coupled to a first client and a second client. The second repeater contains a distributed arbiter that predicts whether the first repeater will send a transaction to the second repeater.

Abstract: A bus arbitration method within a control chipset, The control chipset further comprises a first control chip and a second control chip, data are transferred between the first and the second control chips through a bus, the bus comprises a bidirectional bus The first control chip usually control the authority to use the bus, however the second control chip has higher priority to use the bus. Accompany with a bus specification without waiting cycle, to arbitrate the authority to use the bus can be done fast and without errors. Therefore, no GNT signal line is required and the arbitration time reduces.

Abstract: A method of adjusting an access sequencing scheme for a number of PCI (Peripheral Component Interconnect) compliant units coupled to a PCI bus system on a computer system. These PCI-compliant units are associated respectively with a set of request signals that allow these PCI-compliant units to request the use of the PCI bus system for data transfer. The access sequencing scheme includes a first-layer access sequence loop and a second-layer access sequence loop, with the first-layer access sequence loop having a higher priority over the second-layer access sequence loop The request signals are assigned to either the first-layer access sequence loop or the second-layer access sequence loop in a predetermined manner. The user can change the assignment of a certian request signal from one loop to the other through PC's BIOS (Basic Input/Output System), so as to allow the associated PCI-compliant unit to have a higher priority level to the use of the PCI bus system.

Abstract: When a high-level bus converter receives a normal request from any one of a plurality of intermediate-level bus converters, the high-level bus converter converts the normal request into a retry response and sends the retry response to the intermediate-level bus converter, if a normal response buffer is busy. When the high-level bus converter receives an urgent request, the high-level bus converter sends a normal response in response to the urgent request to the intermediate-level bus converter. Each of a plurality of low-level bus converters issues a normal request, converts, when a retry response is received, the retry response into an urgent request, and reissues a request as the urgent request. When a plurality of urgent requests compete with each other for being processed, each of the plurality of intermediate-level bus converters arbitrates among the plurality of urgent requests, and directly transfers a winner urgent request to the high-level bus converter.

Abstract: A CPU includes a number of functional units that cooperate together to execute instructions. On-chip memory is divided into several sections, each of which is connected to an associated internal bus. All of the functional units are connected to each of the internal busses so that each of the functional units can read from and write to all memory locations. To conduct a transaction with memory, a functional unit determines which memory location it requires, and then arbitrates for mastership of the bus associated with the section of memory containing that memory location. By providing two or more internal busses, two or more bus transactions can occur simultaneously. A virtual bus is provided to facilitate transactions between functional units. The virtual bus is a bus arbiter without an associated physical bus.

Abstract: In a data processing system, a plurality of modules connected to a system bus thereof are assigned with identifiers. When a source module initiates a split read access to another module, the source module sends an address of the access destination module and an identifier of the source module. When sending a response to the source module, the destination module returns response data and the identifier of the source module thereto. Checking the identifier from the destination module, the source module determines the response data returned as a response to the initiated access.

Abstract: A method of configuring a computer system having a processor coupled by a host bus to first and second bus devices causes the processor to transmit on the host bus one or more configuration write commands that include configuration data representing a range of addresses assigned to the second bus device. The configuration data is stored on the first and second bus devices. The processor transmits on the host bus a transaction request directed to an address within a range of addresses assigned to the second bus device. The first bus device determines that it should not transmit a response to the transaction request based on the configuration data stored in the first bus device. The first bus device may include a set of configuration registers for storing configuration data regarding the first bus device and a set of shadow configuration registers for storing configuration data regarding the second bus device.

Abstract: A shared bus arbitration scheme for a data communication system is provided, where a shared bus is connected to a plurality of bus masters and resources, some resources having higher priority than the others and including a peripheral device. Each master may request control of the shared bus and is adapted to perform short transfers and long burst transfers on the shared bus between a resource and the master. A shared bus arbiter is utilized for dynamically determining the highest priority request between a number of shared bus requests, and granting control of the shared bus to the highest priority requesting bus master.

Abstract: An on-chip monitoring circuit is composed of a plurality of individually addressable nodes that are connected together in a circuit which extends from an external data port to each of the monitored circuit points. Address and enable information is passed from node to node. Each node contains address decoding circuitry and enable generation circuitry. As a node receives address information, it decodes part of the address information and enables some of the nodes connected to it, passing the remainder of the address information to the enabled nodes. This process continues until an end node is reached which is connected to the circuit point which is to be monitored. Data generated at the monitored point is passed back though the enabled nodes to the external data port.

Abstract: A method and apparatus allowing two independent arbiters which do not directly talk to one another to function on a common system bus, allowing efficient operation of a master controller, and virtually endless capability to add peripherals to the common system bus without problems or major modifications commonly associated with additional arbitration overhead. A master controller sets time slot parameters for an external, subordinate arbiter as often as desired. Based on the time slot parameter information, the subordinate arbiter functions on an electrically separated portion of the common system bus during all times but for a time slot associated with communication of the super arbiter over the entire common system bus. During this time, a tri-state buffer element allows communication between portions of the common system bus.

Abstract: In the context of a bus-mastering system, a device selector selects the device to control the bus by assigning “combined” priority values to the devices and selecting the device with the highest combined-priority value. The combined-priority values include relatively high-significance device-specific values and relatively low-significance arbitrary-rank values. At any given time, no two devices share the same arbitrary-rank values, and thus cannot share combined-priority values. Thus, there are no unresolved selections due to equal priorities. In accordance with the present invention, the arbitrary-rank values are varied in a round-robin fashion to minimize the bias inherent in conventional schemes using a priority encoder. This makes the device selection process conform better to the device-specific values, which are presumable selected to optimize system performance.

Abstract: A method and apparatus for bus arbitration wherein each bus agent is assigned a weight that governs the percentage of bandwidth allocated to the agent. In addition, each bus agent may also raise the priority of its request based on the amount of time that agent's request has not been serviced. Specifically, the waiting period for the agent is selected so that the agent would be guaranteed access to the bus such that a worst case latency constraint is satisfied. Finally, the arbitration scheme of the present invention can be split into multiple levels of hierarchy, such that when an agent wins arbitration at one level, it is passed to the next higher level where it competes with other agents for bus access.

Abstract: The invention prevents data transfer in a computer network from being sent via a path incapable of transfer or of poor data transfer efficiency. A central processing unit, a main memory unit, and storage devices for storing data and data processing devices are connected in the network, and the data is transferred mutually between the storage devices and the data processing devices without passing through the central processing unit or the main memory unit. The apparatus includes a data transfer control module that identifies the capability/incapability of data transfer based on the physical positions of the storage devices, the physical positions of the data processing devices, and the transfer paths incapable of data transfer. The volume management module specifies a combination of storage devices capable of data transfer based on the physical positions of the storage devices, the physical positions of data processing devices, and the transfer paths capable of data transfer.

Abstract: A PCI-to-PCI bridge having a processor configured for performing various routing mode operations based upon the addresses of transactions carried on interconnected PCI buses. The various routing modes operate on decoded PCI addresses and are known as “programmable decode modes.” In one programmable decode mode, private address spaces are defined for allowing two or more devices interconnected to a secondary PCI bus to communicate directly using private transactions. In another programmable decode mode, subtractive routing operations are provided wherein a secondary PCI interface captures any transactions not claimed on the secondary PCI bus after a predetermined number of clock cycles. Another programmable decode mode is “intelligent” bridging wherein conventional inverse positive decode operations are disabled for the entire primary address space of the secondary PCI bus.

Abstract: A bus arbitration system includes a first priority grant signal determination part for primarily determining a priority grant signal among two groups including a plurality of priority request signals, and a second priority grant signal determination part for finally outputting the priority grant signal among the priority request signals enabled by the first priority grant signal determined from the first priority grant signal determination part. Such a bus arbitration system adopts both the daisy-chain arbitration mode and the round-robin arbitration mode organically. This allows the devices of different characteristics to use the bus line to be suitable for their characteristics, thereby improving throughput of the bus arbitration.

Abstract: A method of configuring a computer system having a processor coupled by a host bus to first and second bus devices causes the processor to transmit on the host bus one or more configuration write commands that include configuration data representing a range of addresses assigned to the second bus device. The configuration data is stored on the first and second bus devices. The processor transmits on the host bus a transaction request directed to an address within a range of addresses assigned to the second bus device. The first bus device determines that it should not transmit a response to the transaction request based on the configuration data stored in the first bus device. The first bus device may include a set of configuration registers for storing configuration data regarding the first bus device and a set of shadow configuration registers for storing configuration data regarding the second bus device.

Abstract: A data processing apparatus with a hierarchical bus for realizing appropriate data transfer speed and data processing speed, even if more I/O devices are connected to the data processing apparatus. Processors are provided in a part or all of the layers in the hierarchical bus. The processors perform selection, projection, and accumulation of data transmitted from I/O devices to a main memory. Accordingly, the quantity of data transmitted to a system bus at an upper layer can be reduced, and the quantity of data processed by the central processing unit can be reduced.

Abstract: A verification system and method for verifying operation of an HDL (Hardware Description Language) design of a computer system component are disclosed. The computer system is configured to interface between a first bus and second bus. During verification, a simulated model of the HDL design is coupled to a simulated first bus and a simulated second bus. A designated stimulus is applied to the simulated model through the simulated first bus. A stimulus file stored in the computer system memory is configured to specify the designated stimulus to be applied. In response to the designated stimulus, the simulated model initiates bus cycles on the simulated second bus. A transaction checker is provided in the computer system memory to receive information relating to these bus cycles from said simulated second bus.

Abstract: A data storage system wherein a main frame computer section having main frame processors for processing data is coupled to a bank of disk drives through an interface. The interface includes a bus having: an bus-select/address/command portion; bus-grant/data/clock-pulse portion; a bus queue portion; and an ending-status portion. A plurality of addressable memories is coupled to the bus. A plurality of controllers is coupled to the bus. Each one thereof being adapted: to assert on the bus-select/command/address portion of the bus, during a controller initiated bus select assert interval, a command. The addressed memory is adapted to produce on the queue portion of the bus a queue signal a predetermined time after a controller initiated bus select assert interval. The queue signal terminates the bus select interval. Another one of the controllers is adapted to provide on the bus-select/address/command portion of the bus another address and command after the queue signal terminates the bus select assert interval.

Abstract: A computer system avoids livelock conditions on a computer bus coupled to plural bus masters. In response to receiving a transaction request from a first bus master across the computer bus, a bus controller transmits a retry command to the first bus master if the bus controller is unable to execute the transaction request. A livelock condition is avoided by preventing transaction requests from any of the bus masters, other than the first bus master, from being processed until after the first bus master re-submits the transaction request. The bus controller may prevent execution of the transaction request from the other bus masters by transmitting retry commands to all bus masters that submit transaction requests after the transaction request from the first bus master is received and before the first bus master re-submits the transaction request.

Abstract: The object of the present invention is to eliminate, in a data processing system having multiple buses, a combination of devices that can not be accessed via a PCI to PCI bridge. When an access request is issued to an S.sub.-- ISA device by an S.sub.-- PCI device, a PCI to PCI bridge determines whether or not a requested address is outside a blocked area, and whether or not the address matches an address stored in a retry register. When the requested address does not match the address in the retry register, the PCI to PCI bridge mistakes the access request for an access to a P.sub.-- PCI device. Thus, the PCI to PCI bridge positively decodes the access request on the S.sub.-- PCI bus, and transmits an access request on the P.sub.-- PCI bus. However, since none of the P.sub.-- PCI devices do not decode the request, the PCI to PCI bridge has to terminate the bus cycle on the P.sub.-- PCI bus by master abort.

Abstract: An apparatus for and a method of arbitrating a stream of access requests over multiple outputs. In one embodiment, the apparatus is implemented with D*[W+(N+1)log.sub.2 D] storage elements, where D is a maximum number of outstanding requests allowed by an issuing agent, N is a number of different request types, and W is a width of access requests measured in bits. The present embodiment comprises a main queue, an input address selection circuit coupled to the main queue for selecting storage locations to receive a stream of access requests, and a plurality of output address selection circuits coupled to the main queue for selecting storage locations to be read. Significantly, the input address selection circuit includes an input address list pointing to vacant storage locations in the main queue, and the input address list is updated each time an access request is stored in, or read out from, the main queue.