Unisys Corporation

Conrad S Shimada

Kelvin S Vartti

James A Williams

Robert H Andrighetti

Donald C Englin

Mitchell A Bauman

John Steven Kuslak

Kenneth L Engelbrecht

Lawrence R Fontaine

Stephen Sutter

William L Borgerding

Chad M Sonmore

A system and method are provided for detecting and recovering from errors in an Instruction Cache RAM and/or Operand Cache RAM of an electronic data processing system. In some cases, errors in the Instruction Cache RAM and/or Operand Cache RAM are detected and recovered from without any required interaction of an operating system of the data processing system. Thus, and in many cases, errors in the Instruction Cache RAM and/or Operand Cache RAM can be handled seamlessly and efficiently, without requiring a specialized operating system routine, or in some cases, a maintenance technician, to help diagnose and/or fix the error.

System and method for detecting and recovering from errors in an instruction stream of an electronic data processing system

A system and method for pre-fetching data signals is disclosed. According to one aspect of the invention, an Instruction Processor (IP) generates requests to access data signals within the cache. Predetermined ones of the requests are provided to pre-fetch control logic, which determines whether the data signals are available within the cache. If not, the data signals are retrieved from another memory within the data processing system, and are stored to the cache. According to one aspect, the rate at which pre-fetch requests are generated may be programmably selected to match the rate at which the associated requests to access the data signals are provided to the cache. In another embodiment, pre-fetch control logic receives information to generate pre-fetch requests using a dedicated interface coupling the pre-fetch control logic to the IP.

Data pre-fetch system and method for a cache memory

A system and method is provided to selectively flush data from cache memory to a main memory irrespective of the replacement algorithm that is used to manage the cache data. According to one aspect of the invention, novel 'page flush' and 'cache line flush' instructions are provided to flush a page and a cache line of memory data, respectively, from a cache to a main memory. In one embodiment, these instructions are included within the hardware instruction set of an Instruction Processor (IP). According to another aspect of the invention, flush operations are initiated using a background interface that interconnects the IP with its associated cache memory. A primary interface that also interconnects the IP to the cache memory is used to simultaneously issue higher-priority requests so that processor throughput is increased.

Cache flush system and method

An improved system and method are provided for initializing memory in a data processing system. According to one aspect of the invention, a 'page zero' instruction is provided that may be executed by an Instruction Processor to initiate memory initialization. Upon instruction execution, the IP issues one or more page zero requests using a background interface of the IP. In one embodiment, each request results in the initialization of a page of memory. While page zero requests are issued over the background interface, the IP may continue issuing other read and write requests to memory over a primary interface of the IP.

System and method for initializing memory within a data processing system

An apparatus for and method of improving the efficiency of a level two cache memory. In response to a level one cache miss, a request is made to the level two cache. A signal sent with the request identifies when the requester does not anticipate a near term subsequent use for the requested data element. If a level two cache hit occurs, the requested data element is marked as least recently used in response to the signal. If a level two cache miss occurs, a request is made to level three storage. When the level three storage request is honored, the requested data element is immediately flushed from the level two cache memory in response to the signal.

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Oakdale, MN, United States of America

Conrad S Shimada