Method and apparatus for resolving probes in multi-processor systems which do not use external duplicate tags for probe filtering

Posted at 11:00 am on 09/25/2001 by Dr. Rahul Razdan

A processor of a multiprocessor system is configured to transmit a full probe to a cache associated with the processor to transfer data from the stored data of the cache. The data corresponding to the full probe is transferred during a time period. A first tag-only probe is also transmitted to the cache during the same time period to determine if the data corresponding to the tag-only probe is part of the stored data stored in the cache. A stream of probes accesses the cache in two stages. The cache is composed of a tag structure and a data structure. In the first stage, a probe is designated a tag-only probe and accesses the tag structure, but not the data structure, to determine tag information indicating a hit or a miss. In the second stage, if the probe returns tag information indicating a cache hit the probe is designated to be a full probe and accesses the data structure of the cache. If the probe returns tag information indicating a cache miss the probe does not proceed to the second stage (Full Patent Here).


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