[Beowulf] more news on the Cell

Vincent Diepeveen diep at xs4all.nl
Thu Jun 30 17:35:24 PDT 2005

Regrettably nothing new there.

We already knew it would have 8 SPE's.

There is a lot of questions remaining :
  a) how many integer execution units does it have within each SPE?
  b) "up to 8 floating point instructions per cycle" sounds very 
     impressive for those who do vector work,
     however elsewhere i read it has a 5 cycle 6 issue SRAM cache.
     How many of those floating point units can do both multiplication 
     and add?
     Correct me if i'm wrong. 
     In case of simplistic matrixcalculations or something similar
     that means each 4 cycles it can do 3 multiplies, it needs to load 6
     floats from SRAM and that can give 2 multiplies. 
     Only if you are real lucky already in register you have a 
     value to multiply with. That means it can do in case of not being lucky,
     that it is getting less than 1 flop per cycle per SPU.

Let's optimistically round it off to 1 flop per cycle (butterfly fmul's):
   1 * 4Ghz * 8 SPE's = 32 gflop @4Ghz.

Still awesome, but not close to the claimed 256+ gflop previously.

Finally what i'm really missing is its price if you want to have CELL
processors without needing to cluster PS3's.


At 04:12 PM 6/30/2005 +0200, Eugen Leitl wrote:
>also, see http://www.research.scea.com/research/html/CellGDC05/index.html
>Eugen* Leitl <a href="http://leitl.org">leitl</a>
>ICBM: 48.07100, 11.36820            http://www.leitl.org
>8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE
>Attachment Converted: "g:\internet\eudora\attach\signature137.asc"
>Beowulf mailing list, Beowulf at beowulf.org
>To change your subscription (digest mode or unsubscribe) visit

More information about the Beowulf mailing list