[Beowulf] Clusters just got more important - AMD's roadmap

Mark Hahn hahn at mcmaster.ca
Wed Feb 8 09:15:01 PST 2012

> The APU concept has a few interesting points but certainly also a few major
> problems (when comparing it to a cpu + stand alone gpu setup):
> * Memory bandwidth to all those FPUs

well, sorta.  my experience with GP-GPU programming today is that your
first goal is to avoid touching anything offchip anyway (spilling, etc),
so I'm not sure this is a big problem.  obviously, the integrated GPU
is a small slice of a "real" add-in GPU, so needs proportionately 
less bandwidth.

> * Power (CPUs in servers today max out around 120W with GPUs at >250W)

sure, though the other way to think of this is that you have 250W 
or so of power overhead hanging off your GPU cards.  you can amortize
the "host overhead" by adding several GPUs, but...

think of it this way: an APU is just a low-mid-end add-in GPU 
with the host integrated onto it ;)

I think the real question is whether someone will produce a minimalist
APU node.  since Llano has on-die PCIE, it seems like you'd need only
APU, 2-4 dimms and a network chip or two.  that's going to add up to 
very little beyond the the APU's 65 or 100W TDP...  (I figure 150/node
including PSU overhead.)

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