Re: [Gems-users] CMP set-up

[Mike Marty <mikem@xxxxxxxxxxx>]

> I would like to set-up a CMP with private L1 caches
> and shared L2. How do I set up a network to reflect
> this ?
>

All the CMP protocols included with GEMS release 1.1 use private L1 caches
and a shared L2.  The network will determine how they are connected
together.

> GEMS does not provide a bus based broadcast network
> but a crossbar based broadcast. Why ?
>

Because the GEMS network code was designed to model packet-switched
networks of any topology.  We model an ordered interconnect by using a
hierarchical switch with the root node providing the ordering.

> What kind of issues will arise from using a broadcast
> switch in-lieu of a bus. Can I simulate a bus with
> GEMS.
>

You can implement a bus if you want.  Its been done in Ruby before.

The HIERARCHICAL_SWITCH provides ordering, but the interconnect is not
globally atomic.  Another request from a different processor may reach the
root switch first.  You must handle this in your protocol.  MOSI_SMP_bcast
handles these situations.

--Mike