HD 7950 - really high power consumption

FlyForFun

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Quote from: kaimyu on January 03, 2014, 08:25:19 AM

I have a Gigabyte 7950 WF3 in a rig and it draws almost 400W(!!). The rest of the hardware is low power.

Some low-end 775 mobo + E6300 (dual 1.86GHz) + 3GB ram + IDE hdd

Yes it is the locked 1.25V version (hardware locked it seems) and I should expect higher power but 400W is a bit high...

Thoughts?

Thanks

What is your settings and power supply? it should consume about 250 watt only...

ScaryHash

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Merit: 501

Yeah, I do not believe that extremely overclocking the 7950's produces enough hash power to warrant the power draw either.

If I overclock mine to 1050, computer + 2 cards will draw about 690 W.

Drop them down to stock 925, back down to 550 W, measured in real-time with an APC power backup digital display. The difference is about 75 Kh/s, for 140 W. Not worth it. Shocked

Temps when overclocked go to 86 C for one card, 77 for the other. Without overclocking, they are both at 75 C.

Totally ridiculous.

ineedit

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Merit: 250

Quote from: Wipeout2097 on January 04, 2014, 03:55:13 PM

The fans using so much power !?

...

Sometimes running at full power just isn't efficient. It is a bit of both fan load and GPU core load, at 1.25v full speed they will pull 300W, drop the voltage to the GPU core and memory and it will still pull 275W at full load. Back it off slightly so the fans are around 3,000 rpm and they will draw 200w, you will lose 40-50KH/s but save 75W.

I have three running in a rig at 750W at the wall averaging 630KH/s each. What I have lost in hash I have saved in watts and greatly extended the lifetime of the cards.

Wipeout2097

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The fans using so much power !?

From what I've read, power use is linear with clock speed but quadratic with voltage. In a very crude calculation, if my 7970 is pulling 13A from the VDDC line PSU at 1V, 1Ghz, that's already 156 W.

See how many Amps (A), Gpu-z is reporting on the Sensors tab, "VDDC current In". Then consider another 30% for the remaining of the card (VDDC is only the GPU core afaik)

So, 1.25(v) * 1.25 * 156(mine) * 1.15(clock) * 1.3 = 365 W

ineedit

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Quote from: kaimyu on January 04, 2014, 08:49:47 AM

100% all the time
Core is around 77C @ 1150/1248

TaDa!

The fans are the problem, you can drop the voltage as low as you like, it is the fans that are drawing the power. You need to solve your cooling problems to get you power usage down.

kaimyu

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100% all the time
Core is around 77C @ 1150/1248

ineedit

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Quote from: kaimyu on January 04, 2014, 06:21:18 AM

I confirmed it tonight - the F43 bios does nothing for me other than change the numbers in GPU-Z. Actual measurements directly from the card stay exactly the same.

Sad

What rpm are your fans at?

kaimyu

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I confirmed it tonight - the F43 bios does nothing for me other than change the numbers in GPU-Z. Actual measurements directly from the card stay exactly the same.

Sad

empoweoqwj

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Quote from: kaimyu on January 03, 2014, 09:34:48 AM

I've tried but I still couldn't change the voltage in Gigabyte's OC guru or in cgminer.
After the bios flash, the voltage was lower in GPUZ but still the same power consumption and voltage at the core using a multimeter.

That's weird the power consumption is the same despite the lower voltage. Something must be going wrong somewhere, or being reported wrong.

ineedit

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Activity: 252

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Quote from: kaimyu on January 03, 2014, 09:34:48 AM

I've tried but I still couldn't change the voltage in Gigabyte's OC guru or in cgminer.
After the bios flash, the voltage was lower in GPUZ but still the same power consumption and voltage at the core using a multimeter.

FYI, The F43 BIOS is from the Gigabyte site and is for the WF3 card, the warranty will not be invalidated.

You will not get the same performance on a Rev 2 card without the fans running at full power, they are nowhere near as good as the Rev 1.0 cards. My last Rev 2.0 card is in a 3 card rig with two Rev 1.0's. The Rev 1.0's are running at 650KH/s @ 72c with 3,000 rpm, the Rev 2 runs at 538KH/s @ 80c with the fan at 3,900 rpm just to get a viable set of watts at the wall

kaimyu

newbie

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I've tried but I still couldn't change the voltage in Gigabyte's OC guru or in cgminer.
After the bios flash, the voltage was lower in GPUZ but still the same power consumption and voltage at the core using a multimeter.

ungaro59

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Yes the only solution is to update the bios. But you risk losing the warranty.
I can change the voltage with "sapphire Trixx" but I do this for each card when the computer restarts.. Undecided

ineedit

sr. member

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Quote from: kaimyu on January 03, 2014, 09:03:58 AM

Unfortunately I can't on my card, it is hardware locked.

Sounds like the card is a Rev 2.0 so use the F43 BIOS from Gigabyte's site, it will drop the voltage to 1.090.

kaimyu

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Unfortunately I can't on my card, it is hardware locked.

ungaro59

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i have the same issue with my Sapphire 7950 OC 1,25V :

https://bitcointalksearch.org/topic/m.4241971

No really solution to automate undervolt.

It necessary to undervolt cards.

kaimyu

newbie

Activity: 42

Merit: 0

I have a Gigabyte 7950 WF3 in a rig and it draws almost 400W(!!). The rest of the hardware is low power.

Some low-end 775 mobo + E6300 (dual 1.86GHz) + 3GB ram + IDE hdd

Yes it is the locked 1.25V version (hardware locked it seems) and I should expect higher power but 400W is a bit high...

Thoughts?

Thanks

Topic: HD 7950 - really high power consumption (Read 3618 times)