Re: [A51] Question about using PS3 hardware

2011-04-25 Thread Cal Leeming [Simplicity Media Ltd] 
On 25/04/2011 21:18, Sylvain Munaut wrote:
 Hi,

 Apologies if this subject has already been covered, but has anyone attempted
 to do table generations using PS3 hardware?
 I did a few back-of-the-enveloppe calculation and it ended up being in
 the same order of magnitude as the ATI GPU cards ... but less
 convenient (need to re-implement / re-test / re-rebug and not really
 faster), so I didn't pursue.
Did it work out cheaper to use PS3 hardware, in terms of physical cost?


 On a side note, have all the
 tables now been generated, or are there still some outstanding?
 all the tables ?

 AFAIK It's a statistical attack, it's never complete, each new table
 helps converge towards 100% success without ever reaching it (and with
 a diminishing return for each new table).

This might be a silly question but, what is the recommended minimum and 
maximum total tables?
Or, can you give an X number of tables will give you X percentage 
chance of success answer?


 Cheers,

  Sylvain

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Re: [A51] Question about using PS3 hardware

2011-04-25 Thread sascha . krissler 
On Mon, Apr 25, 2011 at 10:18:11PM +0200, Sylvain Munaut wrote:
 Hi,
 
  Apologies if this subject has already been covered, but has anyone attempted
  to do table generations using PS3 hardware?
 
 I did a few back-of-the-enveloppe calculation and it ended up being in
 the same order of magnitude as the ATI GPU cards ... but less
 convenient (need to re-implement / re-test / re-rebug and not really
 faster), so I didn't pursue.
 

The performance on the Cell should be quite bad:

6 * 128bit ALU @ 3ghz
versus
320 * 160bit ALU @ 750mhz (HD5870)

together with the fact that the PS3 has way to little RAM for the index
files. So you could use it for generation, but since that phase is now
over, why bother. Once there was the plan to put some Cell blade clusters
to work, but it was abandoned after some initial testing of an incomplete
version of the generator. What we learnt was that it could be done,
development on PS3+linux is quite comfortable. Last time i checked, the
Cell architecture was a dead end and the current hardware is simply too
old for HPC (if you do not happen to have your code running on an existing
cluster, in that case the cost of migration may be uneconomical).
As a sidenote the ration of SRAM to ALUs is also higher on the cell compared
to GPU, be it nvidia or ati, consequently the MIPS per square millimeter
is lower for problems which do not need excessive amounts of cache memory
like A5/1 crypto.
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