Re: [Gems-users] which protocol can I use?


Date: Wed, 26 Mar 2008 09:19:40 +0000
From: Huan Fang <huanf@xxxxxx>
Subject: Re: [Gems-users] which protocol can I use?

By default, the *CMP* protocols treat the caches on a single "chip" as shared. You can change this behavior by changing the map_L1Cache_to_L2Cache (or something like that) in ruby/slicc_interface/ruby_slicc_component_mapping.h. In fact there might even be a function called map_L1Cache_to_PrivateL2Cache still in there. If not, consider adding it. The *SMP* protocols use a single cache controller to model both L1 and L2 caches. Hence L2 caches must be private and exclusive with the L1s.

The *CMP* protocols have more complexity because they support Multiple-CMP systems.

I believe there is an SCMP protocol that is for single-chip use. It has separate L1 and L2 cache controllers. You would have to change the mapping function to make the L2 private.
I am interested in this SCMP protocol,what's the difference with *CMP* ones. If we make L2 private, do we need seperate L1 & L2 controllers? maybe it can use single controller like *SMP* protocols?
--Mike


On Mon, Mar 24, 2008 at 7:30 AM, Huan Fang <huanf@xxxxxx <mailto:huanf@xxxxxx>> wrote:

    Hi everyone,

    It's my first post here :) I need some help to decide which protocol
    best suits my project.
    Since we are considering a CMP architecture with 16 processors on one
    chip, but each processor has its private L1,L2, even memory,(the
    memory
    is shared but physically distributed), shall I use
    MSI_MOSI_CMP_directory or MOESI_CMP_directory? However, they have two
    level directories, do we need the L1-L2 cache coherence protocol?
    Maybe we can use MOESI_SMP_directory, because it's said "The SMP
    protocols can be used to model a CMP with Private caches."
    Any reply are welcome. Thank you.

    Regards,
    Huan
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