[Beowulf] Re: Beowulf Digest, Vol 55, Issue 2

[Craig Tierney]

... stuff deleted

> 
> AMD FIRESTREAM 9250 STREAM PROCESSOR (P/N: 100-505563)        $880
> VISIONTEK RADEON HD4870X2 2GB PCI-E (P/N: 900250)                      $575
> VISIONTEK RADEON HD 4870 512MB PCI-E (P/N: 900244)                     $355
> 
> The 4870 and X2 also run the AMD code.
> 
> So, given a decent machine, with 4 cores and a pair of the 4870X2, one 
> can achieve some pretty amazing GPU
> performance levels for a system well under $4,000.
> 
> With dualX2s ( 4 GPU engines) around $4700 ( extra PSU capacity and 
> cooling is needed for that level).
> 
> I hear that AMD have a new Firestream coming, with the 48x0 family chips 
> on it, but that will likely be a bit on the pricier side..
> 
> Anyway, the Firestream has GPUs with Double-Precision Floating Point.
> Something the  nVidia offerings do not.
> 
> Worth considering.
> 

This is not correct.  The NVIDIA GT200 series supports IEEE DP FP in hardware.
NVIDIA only has 1 DP FP unit per streaming processor (24 on the GTX280) which is
1/8 the number of units of single-precision floating point (each thread has its
own unit).  So the max DP FP rate on a GTX280 is about 90 Gflops.

Does anyone know the peak bandwidth of the new Firestream cards?  I looked around
and all I could find is that it uses GDDR3.  The wikipedia entry says the max
bandwidth of the 9250 is 63.5 GB/s.  This is less than half the GTX280 (max at
140 GB/s, measured using stream like app at 115 GB/s).  If it
is true, the GTX280 may be better for memory bound codes.  That is, if we can
write efficient code for them and leave the whole problem on the GPU to avoid
memory bandwidth issues across the bus.

Craig



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-- 
Craig Tierney (craig.tierney at noaa.gov)