[Beowulf] Has DDR IB gone the way of the Dodo?

Mark Hahn hahn at mcmaster.ca
Fri Oct 3 10:00:05 EDT 2008


>> Has DDR IB gone the way of the dodo bird and been supplanted by QDR?
>
> I don't think front side busses are fast enough for QDR yet.

qdr would be 40 Gb (raw data rate, right?  so 4 GB/s before any sort
of packet overhead, etc.)  I don't really see why that's a problem - 
even a memory-constrained current-gen Intel box has about twice 
that much memory bandwidth available.  AMD or next-gen-Intel will
be even less constrained.

otoh, I rarely see workloads that are clearly net-bw-limited even 
on 4-core myrinet 2g machines - and that's only about 250 MB/s.

regards, mark hahn.
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