The E state has clean data, but the cache is the owner. So it must send the PUTX to give ownership back to the memory. (The memory assumes that the data may be modified when it gives up ownership, because the cache can silently go from E to M on a write.)
...Greg
Edward Lee wrote:
Hi,
In MOESI_SMP_directory protocol, after an L2 replacement E state
issues a PUTX. As far as I know, E state has the clean data which
means memory also has the most recent copy. So, why not just do like
what S state does in this scenario which is, r(Deallocate L2 cache
block. Sets the cache to not present, allowing a replacement in
parallel with a fetch) and then go to I state?
Any ideas?
Regards,
Ed
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