[Beowulf] RDMA NICs and future beowulfs

Mark Hahn hahn at physics.mcmaster.ca
Tue Apr 26 18:45:51 EDT 2005


> Obviously clever governments, who currently have giants of supercomputers
> which costs several million, will conclude they can buy a few cheapo cell
> processor machines which do more work than the entire system currently.

this is ridiculous.  the Cell is basically a GPU - slightly more general
than the current-gen GPUs from Nvidia and ATI, but not drastically different.

similar to GPUs, it is of interest to small niches of people who do
non-graphics computing.  for instance, Cell might be very good for people
doing some kinds of MD or dense-cluster cosmology.  it's *NOT* going to 
change the supercomputing industry.

actually, I'm pretty disappointed with Cell.  from the rumors it's gotten
in preceeding years, I thought they were going to do something truely 
interesting, scalable, novel.  but it's just replicated func-units treated
as a coprocessor to otherwise off-the-shelf parts.  yes, some slightly 
exotic (the rambus angle - but NV/ATI use gddr3 today which is also exotic
but technically off-the-shelf.)  no processor-in-memory innovation,
no clever scalable network, etc.

> To give example the dutch government has a 2.2 tflop 416 processor itanium2
> 1.3Ghz. I do not argue either that it is 2.2 tflop, just like i do not
> argue that a cell processor delivers > 0.25 gflop on its own.

tflops (alone) is a stupid way to measure computers.  that's the real point:
tflops need to be balanced with good memory bandwidth, latency, capacity,
good interconnect, good IO.  not to mention good tools and libraries.

besides, Cell appears to be more like 25 Gflops (doubles, of course):
http://www.mdronline.com/mpr_public/editorials/edit19_09.html

> Just 10 cell processors are faster than the theoretical peak a 416
> processor machine delivers. This for far under 1/1000 of the price that
> this machine has cost.

yeah, I bet SGI is just kicking themselves for not realizing they could just
clamp a few numalink4 cables onto a Cell chip...

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