GPU crunching and memory (amount & type)


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Questions and Answers : GPU applications : GPU crunching and memory (amount & type)

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Profile S@NL - Eesger - www.knoop.nl
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Message 986051 - Posted: 2 Apr 2010, 10:08:49 UTC
Last modified: 2 Apr 2010, 10:10:23 UTC

I am thinking of buying an GT 240, it's power consumption is quite low (max 70 Watt, so that I won't need to buy an new PSU).

But what would the difference in "SETI-performance" be between:

- DDR5 with 512Mb
- DDR3 with 1Gb
- GDDR5 with 1Gb

There is some price difference, but would it be worth it "SETI wise"?
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Message 986117 - Posted: 2 Apr 2010, 16:17:43 UTC - in response to Message 986051.

gddr5 is much faster than the gddr3. Also if you are only running the video card for seti it wont matter much between the 512mb and 1gb of ram. It might affect your performance in high end games though.
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Message 986250 - Posted: 3 Apr 2010, 3:40:29 UTC - in response to Message 986117.

Do you really think it'll affect SETI? I doubt it, I figure 1-5 seconds to load into memory regardless of what type of memory it is, and 15min-hours to crunch depending on the card.

IMO the memory isn't a big deal as much as the speed and cores of the GPU.
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Message 986263 - Posted: 3 Apr 2010, 4:39:51 UTC - in response to Message 986250.

yes the Gddr5 is much faster than Gddr3 otherwise people would quickly figure out that they overpaid for something that isnt better than previous generations of GPU's
my old ATI 2600 XT 512 MB had core clock@ 800Mhz and memory clock @ 900Mhz DDR2
completed Collatz WU's in 2 hours
my newer ATI 4770 512 MB has a core clock@ 750Mhz and memory clock @ 800Mhz GDDR3
completes a Collatz in 17 minutes.
my newer ATI 5850 Black Edition 1 GB has a core clock of 800Mhz and a memory clock of 1125Mhz GDDR5 can complete a Collatz in 6.5 minutes.

The generation of memory most certainly has a lot to do with how fast your card will run

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Message 986280 - Posted: 3 Apr 2010, 7:31:47 UTC - in response to Message 986263.

yes the Gddr5 is much faster than Gddr3 otherwise people would quickly figure out that they overpaid for something that isnt better than previous generations of GPU's
my old ATI 2600 XT 512 MB had core clock@ 800Mhz and memory clock @ 900Mhz DDR2
completed Collatz WU's in 2 hours
my newer ATI 4770 512 MB has a core clock@ 750Mhz and memory clock @ 800Mhz GDDR3
completes a Collatz in 17 minutes.
my newer ATI 5850 Black Edition 1 GB has a core clock of 800Mhz and a memory clock of 1125Mhz GDDR5 can complete a Collatz in 6.5 minutes.

The generation of memory most certainly has a lot to do with how fast your card will run

That may be true of ATI on Collatz. But OTOH I can underclock the memory on my GTX295 by 15% without any noticeable effect on crunch time here on Seti@Home.

Just my 0.02.

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Message 986330 - Posted: 3 Apr 2010, 14:08:52 UTC - in response to Message 986280.

Seti/CUDA doesnt rely on the Memory speed IIRC it relies on the Shaders to process work which is completely independent of the memory speeds
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Message 986406 - Posted: 3 Apr 2010, 20:52:23 UTC - in response to Message 986330.

Seti/CUDA doesnt rely on the Memory speed IIRC it relies on the Shaders to process work which is completely independent of the memory speeds

Exactly so. And the OP was asking if it was worth spending extra for faster memory for SETI...

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Message 986941 - Posted: 5 Apr 2010, 22:18:58 UTC
Last modified: 5 Apr 2010, 22:19:30 UTC

Ehm.. in other words, purly speaking in SETI-performance, it will not be worth the money.. (spending on more/faster memory)?
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Message 987082 - Posted: 6 Apr 2010, 14:55:19 UTC - in response to Message 986941.
Last modified: 6 Apr 2010, 14:58:21 UTC

IMHO, it only makes a difference, if the app fit's completely in GPU-Memory and doesn't need to 'swap'with 'system-memory' or wait on the CPU.
Collatz C. is a good example of this, one HD5770 (1GByteGDDR5) is good for ~80K+
and more, if it allowed >150 WU's (task's) a day.
Seems to me, 80K+ RAC, from one card and a part of a CPU-core, for the loading(= a few seconds), is quite high.
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Message 987097 - Posted: 6 Apr 2010, 15:42:17 UTC - in response to Message 987082.
Last modified: 6 Apr 2010, 15:44:36 UTC

on Milkyway my ATI 5850 gets around 180k a day. this is so much better than even a Nvidia 295. The reason? ATI's full utilization of the GPU memory.

Heck, On DNETC@home they've made special WU's for those of us with ATI 5000 series GPU's. they Quadrupled the work. I get about 5500 credit/WU. Each WU is taking me about 35 minutes now. Score one for ATI.
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Message 987121 - Posted: 6 Apr 2010, 22:19:15 UTC

We seem to go a bit off topic (but I get the distinct impression the difference is delegable for SETI@HOME, therefore the cheapest would suffice..?)

ATI.. haven't paid attention enough I see, there is SETI@HOME ATI-crunching possible, this is the only link I could find. It seems to be just starting out for SETI@HOME.. and only for AP (which is all but abundantly available).. so I think ATI is to early to invest in for S@H (also keeping in mind the mentioned CUDA card only costs about € 75 and uses about 70 Watts tops)
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Message 987129 - Posted: 6 Apr 2010, 22:58:31 UTC - in response to Message 987121.

the easiest way to tell is to look at the top machines that are running seti. It will tell you which GPU is the fastest.
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Message 987496 - Posted: 8 Apr 2010, 14:48:14 UTC

It is quite difficult to correctly figure out what the performance of a GPU is via the 'top machines'..

I thank you all for your input, I have found a cheap GT 240 with 512Mb GDDR5 which should do fine (I hope ;)
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Questions and Answers : GPU applications : GPU crunching and memory (amount & type)

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