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Author Topic: am I doing the right math that 7950 mining at around 100w?  (Read 5321 times)
ryantc
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March 20, 2013, 06:42:32 PM
 #1

after fixing the problem of MSI AB undervolt, I open the GPU-Z and monitor the sensors
it shows the VDDC is 1.028 avg (I set it in MSI at 1.063, below this value some of my cards will just crash sooner or later)
and VDDC Current is bouncing around 95A

So if I remember some high school physics correctly P=UI that gives approx 100w for each card, (I underclock the mem clock to 625 and over clock the core clock to 1000)

or should I use the 12V * VDDC Current In which gives around 115w,

if any of this is true, that's also impressive for a 7950, or did I miss anything?  my physics sucks so that's the best I can derive. Cheesy
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bcpokey
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March 20, 2013, 07:09:04 PM
 #2

I'd believe a kill a  watts more than software numbers, but they're probably reasonably close. Maybe add some overhead for other unreported components of the card other the core, and PSU efficiency in delivering power, and you're running about standard for a 7950. Nice efficient little card.
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March 20, 2013, 08:17:00 PM
 #3

Yeah, measure it at the wall, the heat is electrical inefficiency, which is hard to calculate.

500Mh/s costs me about 160w

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March 20, 2013, 10:22:40 PM
 #4

My cards measure 160-180w at the wall, but only about 110w through those calculations (mining litecoin).  Best to measure at the wall.

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Humanxlemming
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March 20, 2013, 10:56:39 PM
 #5

If you are using some weird math from the specs of the card they are not always 100% right on the box.

Best way to work it out is to get a device that works for your plug socket and then you can work it out so that the math is 100% solid.

If you are wanting uber low power motherboards you should try the FM1/FM2 ones they use next to nothing and they are not that expensive.
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March 21, 2013, 03:09:07 AM
 #6

I think your core is probably using 115W, but once you include the rest of the card and other system inefficiencies, it's probably pulling (from the wall) the 160W other people are saying.

GPU RAM chips require power that prolly aren't calculated by GPUz. The GPU VRMs are inefficient, resulting in a loss of power. Then the computer PSU is also inefficient, resulting in some power draw in the form of heat.

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ryantc
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March 21, 2013, 04:23:36 AM
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Ok, lesson learned,
I did some google search this afternoon, and around 160w is common, but still impressive Cheesy
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March 22, 2013, 12:22:22 AM
 #8

Gigabyte B75 mobo, 4gb ram, Intel G530 + 2xMSI 7950 @0.962V,1000MHZ, 625MHz - 1Ghs - 360w at wall
same config but cards at 950MHZ core/ 1000MHz memory 565khs litecoin - 420w at wall

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ryantc
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March 22, 2013, 12:59:59 PM
 #9

Gigabyte B75 mobo, 4gb ram, Intel G530 + 2xMSI 7950 @0.962V,1000MHZ, 625MHz - 1Ghs - 360w at wall
same config but cards at 950MHZ core/ 1000MHz memory 565khs litecoin - 420w at wall

the voltage is really good, my powercolor 7950 reference won't go lower than 1.063v.....
vdragon
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March 24, 2013, 07:21:30 PM
 #10

Lower than 1.063 at what clocks? Huh

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Humanxlemming
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March 25, 2013, 06:37:07 AM
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I would be careful I have used a few powercool cards they are not the best for overclocking/undervolting.
MKEGuy
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March 25, 2013, 07:19:10 AM
 #12

When we were talking about this on BTC-e I wasn't trying to be a d*** to ya buddy! Smiley  (CNSMining here)  I just know the cards aren't capable of that through my own experiences with mining 7 7970s.

If you have any questions when ou get your 50s going - be sure to check out the mining guide for 5xxx 6xxx 7xxx cards.  Also forum.litecoin.net is a great resource.  BTCe's chat box can turn into a bit of a troll box, so be careful what you listen to over there! Smiley

If you have >100 posts play the Circle of Trust Game  If I have helped you in any way, or you are just feeling generous... please feel free to donate! Smiley LNarfMNLyymkS9WYQFLcmr46AeMYNP8Qj2
ryantc
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March 25, 2013, 03:11:33 PM
 #13

Lower than 1.063 at what clocks? Huh

Currently I am mining ltc at 980/1250 @ 1.063
For btc, I can set it to 980/625 @ 1.050, lower than this may not stable.....
FullLife
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March 25, 2013, 05:27:53 PM
 #14

Gigabyte B75 mobo, 4gb ram, Intel G530 + 2xMSI 7950 @0.962V,1000MHZ, 625MHz - 1Ghs - 360w at wall
same config but cards at 950MHZ core/ 1000MHz memory 565khs litecoin - 420w at wall

What miner and settings are you using?  I haven't been able to get that high w/ those core/mem speeds.
vdragon
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March 27, 2013, 09:23:36 AM
 #15

I am using reaper 13b4

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vdragon
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March 27, 2013, 09:25:15 AM
 #16

Lower than 1.063 at what clocks? Huh

Currently I am mining ltc at 980/1250 @ 1.063
For btc, I can set it to 980/625 @ 1.050, lower than this may not stable.....


 First try using reaper @950/1000, and then experiment with voltage. I have never had a card that must run at that high voltage, max is 1.018 for some shitty piece of gigabyte

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