Influence of the memory frequency on performance

Message boards : Number crunching : Influence of the memory frequency on performance

Author	Message
JM Send message Joined: 18 Mar 09 Posts: 5 Credit: 624,501,954 RAC: 0 Level Scientific publications	Message 28397 - Posted: 3 Feb 2013 \| 20:47:12 UTC
	Hi, I have a GTX 980m and I was wondering if the memory frequency was affecting the crunching performance. I have noticed that a downclock from 1800MHz to 1300MHz is able to lower the GPU temperature by more than 5 degres. But do you think that it changes anything on the overall performance keeping the GPU core clock to the same frequency? I don't see any real difference from the last few results sended but maybe you know more about it technicaly speaking. Thanks for your answers.
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MJH Project administrator Project developer Project scientist Send message Joined: 12 Nov 07 Posts: 696 Credit: 27,266,655 RAC: 0 Level Scientific publications	Message 28400 - Posted: 3 Feb 2013 \| 22:08:15 UTC - in response to Message 28397.
	Derating the memory clock is fine. Done within reason, it should affect performance significantly. MJH
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JM Send message Joined: 18 Mar 09 Posts: 5 Credit: 624,501,954 RAC: 0 Level Scientific publications	Message 28403 - Posted: 3 Feb 2013 \| 23:03:49 UTC - in response to Message 28400. Last modified: 3 Feb 2013 \| 23:04:15 UTC
	Ok thanks. And my mistake it is not a GTX 980m but a GTX 680m. ok so could I monitor a possible loss of performance with the GPU usage? By derating the memory, the GPU core usage (in %) actualy gain 1-2 points compared with the normal frequency. Any explanation?
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werdwerdus Send message Joined: 15 Apr 10 Posts: 123 Credit: 1,004,473,861 RAC: 0 Level Scientific publications	Message 28406 - Posted: 4 Feb 2013 \| 6:26:57 UTC - in response to Message 28403.
	Ok thanks. And my mistake it is not a GTX 980m but a GTX 680m. ok so could I monitor a possible loss of performance with the GPU usage? By derating the memory, the GPU core usage (in %) actualy gain 1-2 points compared with the normal frequency. Any explanation? could be normal variation between 2 different work units ____________ XtremeSystems.org - #1 Team in GPUGrid
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JM Send message Joined: 18 Mar 09 Posts: 5 Credit: 624,501,954 RAC: 0 Level Scientific publications	Message 28407 - Posted: 4 Feb 2013 \| 9:04:59 UTC - in response to Message 28406.
	Yes but in this case same working unit, only the graphic memory clock change..
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Dylan Send message Joined: 16 Jul 12 Posts: 98 Credit: 386,043,752 RAC: 0 Level Scientific publications	Message 28418 - Posted: 5 Feb 2013 \| 23:25:03 UTC
	Done within reason, it should affect performance significantly. I am a bit confused by this, is this statement saying memory clock adjustments won't affect performance, or that they will? In other words, was the word "should" here supposed to be "shouldn't"?
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MJH Project administrator Project developer Project scientist Send message Joined: 12 Nov 07 Posts: 696 Credit: 27,266,655 RAC: 0 Level Scientific publications	Message 28420 - Posted: 5 Feb 2013 \| 23:50:35 UTC - in response to Message 28418.
	Correct: "shouldn't" MJH
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Dylan Send message Joined: 16 Jul 12 Posts: 98 Credit: 386,043,752 RAC: 0 Level Scientific publications	Message 28427 - Posted: 6 Feb 2013 \| 20:41:04 UTC
	Thanks. I'll try adjusting my memory clock on my 670 once the beta tasks are over and I'll post the results I get.
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Beyond Send message Joined: 23 Nov 08 Posts: 1112 Credit: 6,162,416,256 RAC: 0 Level Scientific publications	Message 28525 - Posted: 15 Feb 2013 \| 3:12:30 UTC
	Tried an experiment with my 650 TI, underclocked the memory 300MHz and then increased a little at a time until it was OCed by 300MHz. With every memory clock increase there was a corresponding decrease in completion time. All WUs were the Noelia long type. Total time difference was over 2 hours from lowest to highest memory speed.
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skgiven Volunteer moderator Volunteer tester Send message Joined: 23 Apr 09 Posts: 3968 Credit: 1,995,359,260 RAC: 0 Level Scientific publications	Message 28528 - Posted: 15 Feb 2013 \| 14:07:55 UTC - in response to Message 28525.
	I agree with Beyond's observations. A slight adjustment won't make much difference of course. If GPU-related task crashes are an issue, reducing the GDDR5 clocks a bit is the easiest method of improving stability. Reducing the clocks from 3000MHz by 100MHz won't make a big impact on runtime; it's only 3% slower, so if it stabilizes the GPU it's well worth it. It's probably the case that if you can find stability at a reduced Voltage, even at a slightly reduced memory clock that you will be more efficient in terms of the GPU's performance per Watt. However if you include the rest of the systems overheads you're really shooting yourself in the foot. You would get more value from undervolting a CPU. It's also going to be the case that some cards will yield more from a GDDR OC due to the different bus widths, and thus GPU memory bandwidth. There is going to be some core/shader count/rates vs bandwidth factor, but with varying task requirements it's probably better to be cautious at this time, especially if you are running the test app. ____________ FAQ's HOW TO: - Opt out of Beta Tests - Ask for Help
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Beyond Send message Joined: 23 Nov 08 Posts: 1112 Credit: 6,162,416,256 RAC: 0 Level Scientific publications	Message 28537 - Posted: 15 Feb 2013 \| 20:46:26 UTC
	The particular 650 TI card I bought (MSI Power Edition) has huge memory headroom, the chips are rated much higher than they are clocked by default. SO I feel pretty confident in the memory OC on this particular card. So far no mishaps. As always YMMV.
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Message boards : Number crunching : Influence of the memory frequency on performance

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