On Wed, 24 May 2006, Richard Walsh wrote:
> Greg Lindahl wrote:
> >On Wed, May 24, 2006 at 09:17:58PM +0200, Eugen Leitl wrote:
> >
> >
> >>pGAS assumes shared memory.
Global addressibility in pGAS cannot assume shared memory, or else
pGAS would not be available for clusters.
> >>
> >
> >There's not much point having this discussion when we disagree on
> >such elementary terms.
> >
> >-- greg
> >
> Perhaps a reminder that:
>
> global addressability does not entail global cache coherency
>
> but, we all new that anyway, right?
As for global cache coherency, we agree. The X1 is a "native" pGAS
machine and implements global addressibility *without* enforcing
global cache coherency -- the "native global address space" only
caches accesses to *local* memory, remote reads/writes are not
cached. Global cache coherency runs into some of the scalability
limitations that the Altix faces.
cheers,
. . christian
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