I see, thanks a lot for writing this page!
Jiayuan
> Date: Mon, 10 Dec 2007 10:42:46 -0800
> From: [EMAIL PROTECTED]
> To: m5-users@m5sim.org
> Subject: Re: [m5-users] help with broadcast/snoop handling
>
> On Dec 10, 2007 7:51 AM, Jiayuan <[EMAIL PROTECTED]> wrote:
> > > - You shouldn't be receiving responses from two different caches to a
> > > ReadExRequest no matter what is going on with MemInhibit. Only the
> > > owner cache should be responding, and there shouldn't be more than one
> > > owner at a given point in time.
> >
> > Why is that? The ReadExRequest can be sent from the L1 to the L1-L2 bus
> > after a write miss. At
> > The mean time, this requested cache block might be shared in other L1
> > caches, as well as the L2. Because other L1s are snooping the bus, each
> > cache(L1/L2) containing a copy should send a ReadExResponse back while
> > invalidating its own copy theoretically, (although M5 uses the global
> > pointer to the packet to ensure there is only one response).
>
> All the caches that snoop the packet should invalidate their copies,
> but only the owner should send a response. If there's no owner, then
> main memory will send the response. The fact that there's a single
> shared packet object is used only to emulate two wired-OR lines
> (MemInhibit and Shared). The former is used only to suppress main
> memory from responding, and the latter is used only for setting the E
> state. Those flags are not intended to provide any prioritization or
> arbitration among the caches on the bus (since a real wired-OR line
> isn't capable of that).
>
> There's no need for explicit invalidation acknowledgments since the
> bus provides orderin Your mesh may need that (since you don't have a
> central ordering point), but then that's a different coherence
> protocol. Note that if you want to have multiple responses for a
> given packet, each responder will have to allocate a new Packet... I
> just wrote up a little blurb on memroy allocation for Packets here:
>
> http://www.m5sim.org/wiki/index.php/Memory_System#Packet_allocation_protocol
>
> Steve
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