Coherence index generation for use by an input/output adapter located outside of the processor to detect whether the updated version of data resides within the cache

In a computing system, a method comprising the steps of:

• (a) generating a coherence index by a processor comprising the substep of
• (a.1) in response to a load coherence index instruction executed by the processor, performing in hardware a hash operation to generate the coherence index;
• (b) storing the coherence index in a translation map within an I/O adapter, the I/O adapter not being contained within the processor;
• (c) forwarding the coherence index from the I/O adapter to the processor upon performing a data transfer;
• and,
• (d) upon the processor receiving the coherence index from the I/O adapter in step (c), using the coherence index by the processor to detect whether an updated version of relevant data resides within a cache within the processor, and when the processor detects that an up dated version of relevant data resides within the cache, the updated version of relevant data is used for the data transfer rather than stale data within a main memory which is external to the processor.

A processor comprising:

• a cache;
• and,
• instruction execution means, coupled to the cache, for, in response to an instruction executed by the processor, generating a coherence index to be stored in a translation map within a I/O adapter, the instruction execution means performing in hardware a hash operation to generate the coherence index;
• wherein the I/O adapter is not contained within the processor, and
• wherein when the I/O adapter forwards the coherence index from the I/O adapter to the processor during performance of a data transfer, the processor uses the coherence index to detect whether an updated version of relevant data resides within the cache, and when the processor detects that an updated version of relevant data resides within the cache, the updated version of relevant data is used for the data transfer rather than stale data within a main memory which is external to the processor.