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COHERENT PROXY FOR ATTACHED PROCESSOR

  • US 20140149689A1
  • Filed: 02/26/2013
  • Published: 05/29/2014
  • Est. Priority Date: 11/27/2012
  • Status: Active Grant
First Claim
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1. A method of data processing, comprising:

  • receiving a memory access request from an attached processor (AP) at a coherent attached processor proxy (CAPP) of a primary coherent system, wherein the CAPP includes a CAPP directory of contents of a cache memory in the AP that holds copies of memory blocks belonging to a coherent address space of the primary coherent system, and wherein the receiving includes receiving an expected coherence state of a target address of the memory access request with respect to the cache memory of the AP;

    in response to receiving the memory access request at the CAPP, the CAPP determining a coherence state of the target address with respect to the CAPP and determining whether or not the expected state matches the coherence state determined by the CAPP;

    in response to determining that the expected state matches the coherence state determined by the CAPP, the CAPP issuing a memory access request corresponding to that received from the AP on a system fabric of the primary coherent system; and

    in response to determining that the expected state does not match the coherence state determined by the CAPP, the CAPP transmitting a failure message to the AP without issuing on the system fabric a memory access request corresponding to that received from the AP.

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