Abstract: A router for switching data packets from a source to a destination in a network in which the router includes a distributed memory. The distributed memory includes two or more memory banks. Each memory bank is used for storing uniform portions of a data packet received from a source and linking information for each data packet to allow for the extraction of the uniform portions of a data packet from distributed locations in memory in proper order after a routing determination has been made by the router.

Abstract: A network device switches variable length data units from a source to a destination in a network. An input port receives the variable length data unit and a divider divides the variable length data unit into uniform length data units for temporary storage in the network device. A distributed memory includes a plurality of physically separated memory banks addressable using a single virtual address space and an input switch streams the uniform length data units across the memory banks based on the virtual address space. The network device further includes an output switch for extracting the uniform length data units from the distributed memory by using addresses of the uniform length data units within the virtual address space. The output switch reassembles the uniform length data units to reconstruct the variable length data unit. An output port receives the variable length data unit and transfers the variable length data unit to the destination.

Abstract: A method and apparatus for switching a data packet between a source and destination in a network. The data packet includes a header portion and a data portion. The header portion includes routing information for the data packet. The method includes defining a data path in the router comprising a path through the router along which the data portion of the data packet travels and defining a control path comprising a path through the router along which routing information from the header portion travels. The method includes separating the data path and control path in the router such that the routing information can be separated from the data portion allowing for the separate processing of each in the router. The data portion can be stored in a global memory while routing decisions are made on the routing information in the control path.

Abstract: Snooping is implemented on a split transaction snooping bus for a computer system having one or many such buses. Circuit boards including CPU or other devices and/or distributed memory, data input/output buffers, queues including request tag queues, coherent input queues ("CIQ"), and address controller implementing address bus arbitration plug-into one or more split transaction snooping bus systems. All devices snoop on the address bus to learn whether an identified line is owned or shared, and an appropriate owned/shared signal is issued. Receipt of an ignore signal blocks CIQ loading of a transaction until the transaction is reloaded and ignore is deasserted. Ownership of a requested memory line transfers immediately at time of request. Asserted requests are queued such that state transactions on the address bus occur atomically logically without dependence upon the request. Subsequent requests for the same data are tagged to become the responsibility of the owner-requestor.

Abstract: A split transaction snooping bus protocol and architecture is provided for use in a system having one or many such buses. Circuit boards including CPU or other devices and/or distributed memory, data input/output buffers, queues including request tag queues, coherent input queues ("CIQ"), and address controller implementing address bus arbitration plug-into one or more split transaction snooping bus systems. All devices snoop on the address bus to learn whether an identified line is owned or shared, and an appropriate owned/shared signal is issued. Receipt of an ignore signal blocks CIQ loading of a transaction until the transaction is reloaded and ignore is deasserted. Ownership of a requested memory line transfers immediately at time of request. Asserted requests are queued such that state transactions on the address bus occur atomically logically without dependence upon the request. Subsequent requests for the same data are tagged to become the responsibility of the owner-requestor.

Abstract: In a computer system implementing state transitions that change logically and atomically at an address packet independently of a response, the coherence domain is extended among distributed memory. As such, memory line ownership transfers upon request, and not upon requestor receipt of data. Requestor receipt of data is rapidly implemented by providing a ReadToShareFork transaction that simultaneously causes a write-type operation that updates invalid data from a requested memory address, and provides the updated data to the requesting device. More specifically, when writing valid data to memory, the ReadToShare Fork transaction simultaneously causes reissuance of the originally requested transaction using the same memory address and ID information. The requesting device upon recognizing its transaction ID on the bus system will pull the now valid data from the desired memory location.

Abstract: The present invention provides an "alert" interface for a component which can be safely "hot-plugged/unplugged" to an "alert" interconnect of an electrically powered system. The alert interface has a mating edge which includes daughter precharge/ground connectors, a daughter (engage) waning connector, a number of daughter signal connectors and a daughter engage connector. The alert interconnect includes corresponding mother connectors. The respective connectors of the interconnect and the interface are arranged so that they mate in the following exemplary order when the interface is hot-plugged/unplugged to the interconnect: precharge/ground connectors, warning connectors, signal connectors and finally engage connectors. When the daughter (engage) warning connector mates with the mother warning connector, the component sends an "engage warning" signal to the powered system.

Abstract: A cache tag controller for a cache tag memory for receiving multiple consecutive cache tag modify operations through a system bus to update cache tags in the cache tag memory.

Abstract: A write-back cache control system having a pending write-back cache controller in a multiprocessor cache memory structure. The processor subsystems in the multiprocessor system are coupled together using a high-speed synchronous packet switching bus called a memory bus. Each processor subsystem has an associated cache control system. When a processor's cache control system does not have a required memory location in the cache memory, it broadcasts a memory request packet across the memory bus for the required data. If an owned cache line is being replaced, the cache control system copies the old cache line data to the pending write-back cache controller which is responsible for the write-backs of owned cache lines to main memory. The cache control system then transfers ownership of the old replaced cache line to the pending write-back controller.

Abstract: A time-out detector for a computer system to record any number of time-out events with a predetermined period. The time-out detector comprises A-counter coupled to a transmission medium for incrementing in response to an initiating event and decrementing in response to a terminating event; B-counter coupled to the transmission medium for incrementing in response to an initiating event and decrementing in response to a terminating event; I-state bit coupled to the A- and B- counters for toggling between logic 0 and logic 1 states at each prescale pulse, wherein the logic 0 state causes the A-counter to increment by 1 count at each initiating event, and the logic 1 state causes the B-counter to increment by 1 count at each initiating event; T-state bit coupled to the A- and B- counters for toggling between logic 0 and logic 1 states, wherein the logic 0 state causes the A-counter to decrement by 1 at each terminating event, and if the contents of said A-counter is then equal to 0, the T-state bit is set to 1.

Abstract: A high speed, synchronous, packet-switched inter-chip bus apparatus and method for transferring data between multiple system buses and a cache controller. In the preferred embodiment, the bus connects a cache controller client within the external cache of a processor to a plurality of bus watcher clients, each of which is coupled to a separate system bus. The bus allows the cache controller to provide independent processor-side access to the cache and allows the bus watchers to handle functions related to bus-snooping. An arbiter is employed to allow the bus to be multiplexed between the bus watchers and cache controller. Flow control mechanisms are also employed to ensure that queues receiving packets or arbitration requests over the bus never overflow. A default grantee mechanism is employed to minimize the arbitration latency due to a request for the bus when the bus is idle.