摘要:
The invention is a coherent translation look-aside buffer (TLB) for use in an input/output (I/O) bridge of a symmetrical multiprocessing (SMP) system. The contents of the TLBs may be kept in one of two possible states: exclusive or invalid. When the I/O bridge receives a TLB entry for storage in its TLB, the state of that entry is exclusive. Specifically, the TLB is considered the exclusive owner of the respective TLB entry. The exclusively owned TLB entry may be used by the TLB to translate I/O addresses to system addresses. If some other agent or entity of the SMP system seeks access to the TLB entry (e.g., for purposes of executing a read or write operation), the TLB is notified and the state of the TLB entry transitions to invalid. With the TLB entry in the invalid state, the TLB can no longer use the TLB entry for translating I/O addresses to system addresses.
摘要:
A system and method that reduces the simultaneous switching noise of outputs and the processing delays caused by inductance by using an encoding scheme that results in a net signaling current of substantially zero at each cycle time for the fast parallel switching networks of digital integrated circuit chips and that provides multiple types of error detection.
摘要:
The invention sets forth a crossbar unit that includes multiple virtual channels, each virtual channel being a logical flow of data within the crossbar unit. Arbitration logic coupled to source client subsystems is configured to select a virtual channel for transmitting a data request or a data packet to a destination client subsystem based on the type of the source client subsystem and/or the type of data request. Higher priority traffic is transmitted over virtual channels that are configured to transmit data without causing deadlocks and/or stalls. Lower priority traffic is transmitted over virtual channels that can be stalled.
摘要:
The invention sets forth a crossbar unit that includes multiple virtual channels, each virtual channel being a logical flow of data within the crossbar unit. Arbitration logic coupled to source client subsystems is configured to select a virtual channel for transmitting a data request or a data packet to a destination client subsystem based on the type of the source client subsystem and/or the type of data request. Higher priority traffic is transmitted over virtual channels that are configured to transmit data without causing deadlocks and/or stalls. Lower priority traffic is transmitted over virtual channels that can be stalled.
摘要:
Deadlocks are avoided by marking read requests issued by a parallel processor to system memory as “special.” Read completions associated with read requests marked as special are routed on virtual channel 1 of the PCIe bus. Data returning on virtual channel 1 cannot become stalled by write requests in virtual channel 0, thus avoiding a potential deadlock.
摘要:
A system and method avoids “livelock” and “starvation” among two or more input/output (I/O) devices of a symmetrical multiprocessor (SMP) computer system competing for the same data. The SMP computer system includes a plurality of interconnected processors, one or more memories that are shared by the processors, and a plurality of I/O bridges to which the I/O devices are coupled. A cache coherency protocol is executed the I/O bridges, which requires the I/O bridges to obtain “exclusive” (not shared) ownership of all data stored by the bridges. In response to a request for data currently stored by an I/O bridge, the bridge first copies at least a portion of that data to a non-coherent buffer before invalidating the data. The bridge then takes the largest amount of the data saved in its non-coherent buffer that its knows to be coherent, and releases only that known coherent amount to the I/O device, and then discards all of the saved data.