[Beowulf] Cell

Vincent Diepeveen diep at xs4all.nl
Wed Apr 27 14:04:51 EDT 2005


At 11:07 AM 4/27/2005 -0500, Ben Mayer wrote:
>On 4/27/05, Vincent Diepeveen <diep at xs4all.nl> wrote:
>> At 06:45 PM 4/26/2005 -0400, Mark Hahn wrote:
>> >> 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.
>> 
>> Cell is from my viewpoint a vector floating point processor which only
>> disadvantage is executing branchy code.
>> 
>> Just like Cray machines were in the past vector processors.
>
>Their current machine (X1E) is a vector machine. The problem on that
>machine is that the code needs to vectorize. You can do it with the
>compiler or libraries, but it HAS to vectorize to get that
>performance. Cray's current machines depend on the compiler and highly
>trained humans writing code (they have some libraries for specific
>things like sequence alignment) to make things run faster then a
>Pentium 4. Granted when they do run faster, it is a 32-64x speed up
>*per CPU*.
>
>The people writing code for the PS3 (Cell) are going to have some
>experience writing parallel vector code because that is what the PS2
>was. But I will be very surprised if they can consistently get more
>then 10% of peak.
>
>
>> A gpu doing effectively 256 gflop for just a few dollar would be nice.
>
>GPUs are often time doing calcs at half precision.
>
>> 
>> See supercomputer reports europe.
>> 
>> So there is a BIG need for a CHEAP vector processor doing floating point
>> there.
>
>Is it processors that they need or bandwidth?

If you can deliver 1 processor that can do 1 tflop, there is no need for
bandwidth anymore, everything happens on that chip in such a case :)

"If you were plowing a field, which would you rather use? Two strong oxen
or 1024 chickens?"
  Seymour Cray

Vincent
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