Hello , i tryed and noticed that when i lowering the DRAM frequency

on my two gtx 460 i am saving energy.

But how low should i go ?

Shaders at 1500 mhz and DRAM at 1400 mhz.

Can i continue to lower this frequency or will i get errors ?

Will this effect the completion time of the wu ? or is that

irrelevant to crunshing performance ?

You will have to work that out for yourself. Different cards would be affected in different ways (in terms of performance). Low to mid range cards may be less affected. Lowering the GPU memory will slow the task down a bit, and the more you lower it the more it will slow, but how much will vary by task type and app (3.1/4.2). You may also reach a point were the GPU becomes unstable, or you may find that performance suddenly drops off (bad balance &/or recoverable errors). Up to ~20% doesn't usually result in a big performance drop, but after that further power savings would probably become insignificant.

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ok, i understand there will be suddenly some surprices i wont expect. ok, i will try.

ok, i understand there will be suddenly some surprices i wont expect. ok, i will try.

Well.. you should be able to go quite low before funny things start to happen. However, GPU-Grid performance will suffer from reduced memory speed. So if you go too low you actually lower your overall power efficiency (the GPU gets starved for work but can't go to sleep either).
Back when I was running GPU-Grid I had the memory slightly overclocked.

MrS

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Scanning for our furry friends since Jan 2002

Please post your results as you test. We could all learn something here. When overclocking, the conventional wisdom is that higher memory clocks don't help GPUGrid much. The converse may also be true.

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Thx - Paul

Note: Please don't use driver version 295 or 296! Recommended versions are 266 - 285.

So at the time i have been trying if done this:

At first i must say , it works, a small power saving is there, but its very low to one gpu. Its about 25 watts each card i am using.

Settings for one GTX 460:

Voltage at 937mV
Chipset Frequency at 750 Mhz
VDRAM at 1254 MHz (cant get lower because hardware restriction)
Shaders of course at 2*750 Mhz = 1500 Mhz
As i lowered the VDRAM frequency i have to rise the voltage about 12mV.
Using "Nvidia Inspector" software.

That´s all i can tell at this time.

It was on an Gigabyte GTX 460 OC1G-I 1024MB.



Will that help ? :)

This will help, but you'Ve got to measure performance as well. Average over at least 10 WUs (calculate something like credits/day). Then return to stock, measure performance again and report absolute power draw. For example if you save 5% electricity but crunch 10% slower, then it's not worth it.

BTW: increasing GPU voltage increases power consumption of the main consumer.. I wouldn't do this just to clock the memory lower :p

MrS

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u must be right, overall the 25 watts mean savings by 15,625 percent. calulated with official power consumption data at 160 watts.

but i must crunsh more WU to make an average performance comparsion.

That will take some time, thanks for the advice. Keep crunshing ...

calulated with official power consumption data at 160 watts.

That's the TDP, not what the card is actually using. It's probably using more like 120W.

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i will never check this out, even making a comparsion table in excel is not my strength.

here in germany we say: Never trust a study you have not self faked it. ;)

so what for do this , anyone can watch the results. I´ll never get 100% authenthic data about it.

Taking a look at your PCs.. you might want to try to merge similar ones, which appear multiple times. Makes it easier to look at the right tasks.

And then all we really need is the following data: WU run time + credits granted. We can work out the following numbers for you, no problem. However, if you can't measure the real power consumption, it will be difficult to judge whether downclocking the VRAM was worth it or not. If you could borrow a power consumption measurement device (~15€, became quite popular in the recent years) we could get hard numbers.

MrS

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i have two of them. I also got a second pc , there i can place only one or two pcie graphicscards.

I stop that experiment, on my second pc there was only a power difference of 11 watts by lowering the VDRAM frequency. Very bad i think.

It's normal that the DRAM frequency doesn't impact overall power consumption much. Otherwise we couldn't get away without actively cooling them :)

At Milkyway one can go to really low frequencies, about 1/3 the stock frequency. There it really starts to matter, saving you about 15 - 30 W per card.

MrS

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On a GTX470 I can save 20W by reducing the GDDR from 1700 to 1300MHz.
I don't know what performance difference it will make, but I'm 25% into a Nathan task so I will work it out later.

- It turns out that it's 6% slower.

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courios , back in my system with three gpus i am saving more power than ever. Its again 25 watts or slightly more that a save per gtx 460 gpu !?

How are you measuring these 25W/GPU, Ratanplan?

BTW: if GPU performance suffers from the reduced memory clock, the GPU will also consume less power ;)

MrS

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before and after downclocking the two gtx 460 at full load.

Beforce ~500 watts Now~ 450 watts at "full" load of all gpus.

I could stop crunshing, and set colckinbgs to stock VDRAM frequency,

i try it. Back soon.

Edit:

cant tell now , running two ACEMD 2 , must wait for Long runs.

In three hours i got 3 Long Runs running, can tell then, if its my fault or real.

Just for reference:
My 20W power saving (from underclocking my GTX470's memory) came at a cost of 6.05% task performance loss. The power usage was measured at the wall socket for the Main System Unit (MSU), running the same tasks (CPU and GPU) under the same settings, only a few seconds after reading it at normal frequency.

Without underclocking the GDDR:
3 NATHAN_RPS tasks at 22,046.59, 22,020.22, 22,031.58

After underclocking the GDDR:
1 NATHAN_RPS task took 23,066 seconds (but had already completed 25% of the task). So basically the remaining 75% took an extra 1000sec, which would mean a full task would take 1333seconds. 23333/22000=1.06 or 6% longer.

My MSU use to use 330W and now uses 310W. So it's now 310/330 more efficient. It just so happens that this is 6.45% which basically means the system isn't any more efficient in terms of tasks completed/Watt; it's just about the same.

If you really accurately measured this and tuned the GPU you might become about 1% more efficient per Watt, but that's about it.

So 'generally speaking' don't underclock here expecting to be more efficient; your just doing less for less electric. If you have multiple GPU's then that 0.4% improvement would increase slightly, but even then your talking about 2 or 3% more efficient and all this ignores the GPU purchase costs!

I completely expected these results, and I know that overclocking results in the same task performance per Watt; you use more energy but crunch faster (when overclocking without increasing the voltage, and up to ~15% OC). Even with a slight V increase and going up to ~20% the performance per watt is fairly similar, so long as you measure at the wall and use one GPU.

BTW my MSU just uses ~78W idle.

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It must be the computers fault :o/

unbelievable , now the power comsumption wend down from 475 watts to

465 watts, and saves to say absolutly nothing. dont know what happend ? :S

before it got a total power consumption of 500 watts :S