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Author Topic: Fake volt change?  (Read 708 times)
Brunic
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January 27, 2012, 05:29:22 AM
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Hey guys, I have an odd problem.

I have these:
http://www.newegg.ca/Product/Product.aspx?Item=N82E16814131434

I tried to change the voltage with cgminer, atitweak and AMDOverdriveCtrl. They all let me do it, and confirm me that the voltage has been changed. When I check the infos of the GPU, they show the new voltage.

The thing is, it doesn't seem to do anything. With a Kill-a-watt, whatever the value of the voltage is, it is the same consumption. I even tried to clock my card to 850 Mhz with a voltage of 0.1 and it worked! It seems the card doesn't take into account the voltage I try to input.

I can still change the core clock without problems, and see the results (lower/higher hashing and consumption). Same thing for the memory clock, it works like it is supposed to do. But the voltage, I think I could write 100V into it without making any difference.

I use Linuxcoin 0.2final on that rig.
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deepceleron
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January 27, 2012, 05:52:01 AM
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Not all cards have voltage regulators that can be changed by software - that is one of the first things to go when making an economy model. Others use a proprietary method for controlling hardware. I can't speak for that specific card though.

jake262144
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January 27, 2012, 09:32:36 AM
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If the card confirmed 0.1V core voltage and didn't crash instantly, it's obviously lying.

The first thing I do when undervolting is set the minimal core voltage specified by the manufacturer, like 0.95V. If the card is still running and the temperature didn't budge there's just no talking with this particular VRM, no matter what voltage the device is reporting.

I've also seen some weirdness when going from 1.2V downto 1.105V results in no change at all but going to 1.1V automagically drops the temp by 5°C. That means this specific VRM only accepts a few discrete values which you're going to have to identify by hand.
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January 27, 2012, 08:30:22 PM
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Thanks for the help. It seems that there is no VRM on that card. I removed the fan and checked the board to be sure, and the chip doesn't seem to be there.
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January 27, 2012, 08:30:41 PM
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Thanks for the help. It seems that there is no VRM on that card. I removed the fan and checked the board to be sure, and the chip doesn't seem to be there.
lol

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