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Author Topic: Undervolting 5xxx's below 0,95v  (Read 1145 times)
Isokivi
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May 09, 2012, 03:48:06 PM
 #1

Has anyone done this, that would like to share some numbers. Im particularly interested in 5870's and 5970's.

Im currently running a rig with:

  • GPU:  5870, Arctic cooling Accelero Extreme
    Core: 735
    Mem: 150
    Voltit: 0.95
    Mh/s: 310

    GPU:  5870, Arctic cooling Accelero Extreme
    Core: 760
    Mem: 150
    Voltit: 0.95
    Mh/s: 318

    GPU:  5970 1/2
    Core: 730
    Mem: 150
    Voltit: 0.95
    Mh/s: 309

    GPU:  5970 2/2
    Core: 745
    Mem: 150
    Voltit: 0.95
    Mh/s: 313

    GPU: 5970 1/2
    Core: 725
    Mem: 150
    Voltit: 0.95
    Mh/s: 309

    GPU: 5970 2/2
    Core: 695
    Mem: 150
    Voltit: 0.95
    Mh/s: 300

Totaling 1865MHS @ 621W drawn from the wall, for an efficiency of 3,003MHS/J

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May 10, 2012, 06:06:04 AM
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Funny, I just tried this yesterday with my 5850s. I've been running at 0.95 and took them down to 0.90. In my case, at least, the reduction in power consumption wasn't very significant. Sorry, I don't remember the exact difference, but I think it was less than 15w for the four 5850s in my rig. Anyway, I decided not to bother with it and stay at 0.95. But the cards were stable at 0.90 during the time I played around with it, and I took them up to 725MHz, just 25MHz below the core clock I normally use at 0.95. I use atitweak (linux) to set the voltage if you are wondering.
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May 10, 2012, 01:21:04 PM
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Funny, I just tried this yesterday with my 5850s. I've been running at 0.95 and took them down to 0.90. In my case, at least, the reduction in power consumption wasn't very significant. Sorry, I don't remember the exact difference, but I think it was less than 15w for the four 5850s in my rig. Anyway, I decided not to bother with it and stay at 0.95. But the cards were stable at 0.90 during the time I played around with it, and I took them up to 725MHz, just 25MHz below the core clock I normally use at 0.95. I use atitweak (linux) to set the voltage if you are wondering.

Since I see myself facing a situation where I'd prefer to "run my gpu's to the ground" I find myself looking for the utter optimal MHS/W, in advance for the upcoming block-reward drop. It can also be the more profitable way to go for me, 5970 2nd hand markets seem to be getting active around here, most likeley because of new models hitting the market and I fear the situation might get rediculous around the block-reward drop. Personally if I had free electricity I'd make damn sure to have liquidity to invest in to gpu's when the block reward gets chopped down.

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May 10, 2012, 02:34:49 PM
 #4

What if BTC exchange rate doubled when the block reward drops? Nothing happened?

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May 10, 2012, 03:36:38 PM
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Funny, I just tried this yesterday with my 5850s. I've been running at 0.95 and took them down to 0.90. In my case, at least, the reduction in power consumption wasn't very significant. Sorry, I don't remember the exact difference, but I think it was less than 15w for the four 5850s in my rig. Anyway, I decided not to bother with it and stay at 0.95. But the cards were stable at 0.90 during the time I played around with it, and I took them up to 725MHz, just 25MHz below the core clock I normally use at 0.95. I use atitweak (linux) to set the voltage if you are wondering.

Since I see myself facing a situation where I'd prefer to "run my gpu's to the ground" I find myself looking for the utter optimal MHS/W, in advance for the upcoming block-reward drop. It can also be the more profitable way to go for me, 5970 2nd hand markets seem to be getting active around here, most likeley because of new models hitting the market and I fear the situation might get rediculous around the block-reward drop. Personally if I had free electricity I'd make damn sure to have liquidity to invest in to gpu's when the block reward gets chopped down.

I agree - think this is a good strategy, and for those with access to cheap electric it makes more sense than going the FPGA route, at least for a modest size operation. You might also consider 5850s if you can get them cheaper than 5870s. I'm getting 300 Mh/s out of mine at 0.95. I think its worth trying below 0.95 to see if the power saving is worth it for you. Just saying that for my modest rig it didn't really seem worth it. While I want an efficient rig, I also want my rig to run more or less like an appliance that chugs away rock-solid stable without any fuss, and I'm not that motivated to futz around with lower voltages if it's only going to make of difference of 15-20w or so, especially if this means a reduction in hashing rate. Power consumption depends exponentially on voltage, but an exponential curve has a rather flat bit before it ramps up, and I think that when you go below 0.95, you are starting to get into the flat bit where lower voltage doesn't get you as much power savings. This at least is consistent with what I've observed for my rig in playing around with different voltage levels.  

Edit: After playing around a bit more, I'm now skeptical that atitweak is actually lowering the voltage below 0.95. At the same core clock, I see no difference at all in terms of what I'm pulling from the wall when I use atitweak to supposedly drop the voltage from 0.95 to 0.90. The difference I saw before was I think entirely due to a slightly lower clock. Sorry about the confusion - I shouldn't have taken what atitweak was reporting at face value. If anyone knows how to drop 58xx voltages below 0.95 in linux, I'd like to hear about it. 
Isokivi
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May 10, 2012, 03:40:44 PM
 #6

What if BTC exchange rate doubled when the block reward drops? Nothing happened?

That would be sweet, but I try not to make mining assumptions based on wishful thinking. Tbh my pessimistic projection for next year is an average difficulty of 1560000 (10% lower than current) and an average exchnage rate of 6$. The only function of these numbers to me is that I need every single piece of hardware I mine to be profitable at those conditions, or it gets unplugged and sold at some point.

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May 10, 2012, 04:56:54 PM
 #7

15W/h = 131.4kw / Year = ~30$ less Bill  Shocked

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May 10, 2012, 06:16:01 PM
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What if BTC exchange rate doubled when the block reward drops? Nothing happened?

That would be sweet, but I try not to make mining assumptions based on wishful thinking. Tbh my pessimistic projection for next year is an average difficulty of 1560000 (10% lower than current) and an average exchnage rate of 6$. The only function of these numbers to me is that I need every single piece of hardware I mine to be profitable at those conditions, or it gets unplugged and sold at some point.

It's not wishful thinking.  Just look what happened to the exchange rates for Solidcoin and Ixcoin when the block reward diminished.  Turns out alt chains are actually useful in this case since they give us a glimpse of what could happen when Bitcoin block reward halves.

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May 11, 2012, 08:10:20 AM
 #9

[...]
If anyone knows how to drop 58xx voltages below 0.95 in linux, I'd like to hear about it. 
this.

it might be possible by flashing a modified bios. has anyone tried that yet? I am afraid to brick my cards. Maybe somebody has a half broken one to try it on?


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