Re: [Gems-users] 3 hop writeback MESI SCMP

[Mike Marty <mikem@xxxxxxxxxxx>]

You need at least a 2-hop writeback to ensure the L2 writes back dirty 
data to memory before erroneously re-fetching stale data.  This assumes 
possible reordering on the interconnect.  And yes, if you have seperate 
physical links between an L2 bank and its memory controller, then you 
probably wouldn't need a 2-hop or 3-hop writeback nor would you need 
seperate virtual networks.
--Mike


> Hi folks,
>
> Q1) In MESI SCMP why do you need a 3 hop writeback from L2 to memory.
>
> If there's only a single physical link between a given L2 bank and 
> memory module, does it matter that we have separate networks for the L2 
> req to Dir and data-response from L2 to/from Dir.
>
>
>
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