[Beowulf] Intel quad core nodes?

[Jan Heichler]

Hallo Barnet,

Montag, 8. Oktober 2007, meintest Du:

BW> I'm moving towards setting up a small cluster (my first), and am 
BW> thinking about using Intel quad core processors.  However, I'm a little
BW> concerned about memory contention.  I'm (tentatively) going to have one
BW> processor per node (this appears to be the cheapest way to go), but I
BW> still wonder whether four cores will choke Intel's memory architecture.
BW> (AMD's Barcelona may be better in this regard, but it doesn't seem to be
BW> available yet, at least not through retail channels).

Yes intel does have a memory bandwidth problem....

BW> I'd like to hear any opinions on this issue.  And if you've used quad
BW> core processors, I'd certainly like to hear about your experiences
BW> (including which processor you've used).

... but it does not to affect performance as hard as one could think.
How big the impact is depends mostly on your application. I saw code
scaling very good (HPL for example ;-) ) and others where you just get
10% more out of using 8 instead of 4 cores (on a dual socket quadcore
system).

Another aspect that you should think of is the i/o intensity of your
application. Remember that 4 cores in a single socket system will
share the same interconnect port. That could hit performance pretty
bad. A high speed interconnect could be a solution to that problem but
will cost you money.

Conclusion: the only good benchmark is your own application. The Intel
DualCore performs quite good on a wide range of applications. The
QuadCore performs good on some of 'em - but as you said: it seems to
be the only available (through retail channels) quadcore to the market right now...

Regards Jan