Athlon MP vs Athlon XP

Greg Lindahl lindahl at conservativecomputer.com
Thu Nov 8 14:48:52 EST 2001


On Thu, Nov 08, 2001 at 02:28:40PM -0500, Velocet wrote:

> From what I understood from the useful articles that were
> posted here, the cache protocol allows sharing data between the CPUs
> via the northbridge directly.

Right. What it comes down to is this: Getting data from L2 is always
fastest if its in your own L2. But if it isn't, some machines fetch
from main memory faster than they can fetch a dirty line from someone
else's L2. AMD's scheme has reasonably fast main memory fetches, plus
even more efficient fetches from a remote L2.

I believe the Sun E10k is one of the few processors where main memory
is closer than someone else's L2. That makes false sharing even worse
than usual.

However, from the beowulf standpoint, most of us are running 2
independent mpi proceses on dual cpu boxes, right?

g

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