Microunity Systems Engineering, Inc.

William K Zuravleff

Timothy B Robinson

Mark Semmelmeyer

Scott Furman

A non-blocking load buffer is provided for use in a high-speed microprocessor and memory system. The non-blocking load buffer interfaces a high-speed processor/cache bus, which connects a processor and a cache to the non-blocking load buffer, with a lower speed peripheral bus, which connects to peripheral devices. The non-blocking load buffer allows data to be retrieved from relatively low bandwidth peripheral devices directly from programmed I/O of the processor at the maximum rate of the peripherals so that the data may be processed and stored without unnecessarily idling the processor. I/O requests from several processors within a multiprocessor may simultaneously be buffered so that a plurality of non-blocking loads may be processed during the latency period of the device. As a result, a continuous maximum throughput from multiple I/O devices by the programmed I/O of the processor is achieved and the time required for completing tasks and processing data may be reduced. Also, a multiple priority non-blocking load buffer is provided for serving a multiprocessor running real-time processes of varying deadlines by prioritization-based scheduling of memory and peripheral accesses.

Method for storing prioritized memory or I/O transactions in queues

A non-blocking load buffer for use in a high-speed microprocessor and memory system. The non-blocking load buffer interfaces a high-speed processor/cache bus, which connects a processor and a cache to the non-blocking load buffer, with a lower speed peripheral bus, which connects to peripheral devices. The non-blocking load buffer allows data to be retrieved from relatively low bandwidth peripheral devices directly from programmed I/O of the processor at the maximum rate of the peripherals so that the data may be processed and stored without unnecessarily idling the processor. I/O requests from several processors within a multiprocessor may simultaneously be buffered so that a plurality of non-blocking loads may be processed during the latency period of the device. As a result, a continuous maximum throughput from multiple I/O devices by the programmed I/O of the processor is achieved and the time required for completing tasks and processing data may be reduced. Also, a multiple priority non-blocking load buffer is provided for serving a multiprocessor running real-time processes of varying deadlines by prioritization-based scheduling of memory and peripheral accesses.

Non-blocking load buffer and a multiple-priority memory system for

System for placing entries of an outstanding processor request into a

A controller for a synchronous DRAM is provided for maximizing throughput of memory requests to the synchronous DRAM. The controller maintains the spacing between the commands to conform with the specifications for the synchronous DRAMs while preventing gaps from occurring in the data slots to the synchronous DRAM. Furthermore, the controller allows memory requests and commands to be issued out of order so that the throughput may be maximized by overlapping required operations which do not specifically involve data transfer. To achieve this maximized throughput, memory requests are tagged for indicating a sending order. Thereafter, the memory requests may be arbitrated when conflicting memory requests are queued and this arbitration process is then decoded for simultaneously updating scheduling constraints. The memory requests may be further qualified based on the scheduling constraints and a command stack of memory request is then developed for modifying update queues. The controller also functions by receiving a controller clock signal and generating an SDRAM clock signal by dividing this controller clock signal.

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Mountainview, CA, United States of America

William K Zuravleff