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I've been to several PSU power calcs and each one has very different result for 7950 card from 125W to 300W per card.Any help?

Last response: in Graphics & Displays
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November 6, 2013 11:23:20 AM

Tom's hardware says 190 for bitming and I'm interested in gpu mining of scrypt coins and thats why I'll use 6 7950 cards on the mobo.I don't know who to believe.
4gb ddr3 ram
usb stick
h61del motherboard
g1620 cpu
nothing else.

I tried to calculate using several calcs online but the results vary too much.

I want to buy asap
November 6, 2013 11:27:04 AM

190 mining seems close since it is very hard on the card.

This is what Techpowerup got with the 7950s

http://www.techpowerup.com/reviews/AMD/HD_7950/25.html

AMD recommends 750 plus.

Now lets say the cards hit 200 watts each and the cpu is hitting 75(i know it has a TDP of 55)

Add in another 50 for everything else and you are just under 550 watts(as a high guess for a bit of safety margin). Now getting something a bit bigger never hurts and should be good for the unit to not work too hard.

For a normal system I would go on the lower end, but since you are running hard all the time, I would go 650 + just to keep it stable.

AMD's 750 also takes into account higher wattage cpus and you do not even have a hard drive.
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November 6, 2013 11:41:47 AM

nukemaster said:
190 mining seems close since it is very hard on the card.

This is what Techpowerup got with the 7950s

http://www.techpowerup.com/reviews/AMD/HD_7950/25.html

AMD recommends 750 plus.

Now lets say the cards hit 200 watts each and the cpu is hitting 75(i know it has a TDP of 55)

Add in another 50 for everything else and you are just under 550 watts(as a high guess for a bit of safety margin). Now getting something a bit bigger never hurts and should be good for the unit to not work too hard.

For a normal system I would go on the lower end, but since you are running hard all the time, I would go 650 + just to keep it stable.

AMD's 750 also takes into account higher wattage cpus and you do not even have a hard drive.


I don't think I understand your calculations.
I'd do it like this
6x 200W is 1200
+55 for CPU+ x for mobo and rest usb and ram
=1255W + x W

Where am I wrong?
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November 6, 2013 11:49:12 AM

~217W overclocked full load, ~138W stock full load. http://www.guru3d.com/articles_pages/radeon_hd_7950_ove...

I would bank on quality 550W supply, keep the supply around 60% load.

If you literally meant 6 cards, you'll need a different motherboard and something like a 1500W supply.

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November 6, 2013 12:06:31 PM

Eximo said:
~217W overclocked full load, ~138W stock full load. http://www.guru3d.com/articles_pages/radeon_hd_7950_ove...

I would bank on quality 550W supply, keep the supply around 60% load.

If you literally meant 6 cards, you'll need a different motherboard and something like a 1500W supply.



Yes I mean 6 cards
and I'll use powered pci-e risers to avoid burning the mobo
?So are my calculations correct?
how much watts is X?
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November 6, 2013 12:07:39 PM

Why 60% load? I'd rather have it 9?% load so I don't have to pay too much
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November 6, 2013 12:08:17 PM

I want to buy asap
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November 6, 2013 1:10:04 PM

The warmer a power supply runs the less efficient it is, also it will burn out faster.

1500W is the minimum I would use for powering 6 GPUs, maybe 1250W. Even if you go with the minimum you would still be looking at 850W or so without anything else, but these things are going to pump out some serious heat, and the hotter they get, the less efficient the video cards will be themselves. It is not a very common test, so you should err on the side of caution with this much money invested.

Not sure that 1x slots provide enough bandwidth for what you are doing, unless there is a custom driver in Linux or something to let that work, or if bandwidth isn't that important to mining.
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November 6, 2013 1:17:51 PM

Eximo said:
The warmer a power supply runs the less efficient it is, also it will burn out faster.

1500W is the minimum I would use for powering 6 GPUs, maybe 1250W. Even if you go with the minimum you would still be looking at 850W or so without anything else, but these things are going to pump out some serious heat, and the hotter they get, the less efficient the video cards will be themselves. It is not a very common test, so you should err on the side of caution with this much money invested.

Not sure that 1x slots provide enough bandwidth for what you are doing, unless there is a custom driver in Linux or something to let that work, or if bandwidth isn't that important to mining.


I'm trying to understand where did that 850w come from???

since the 6 cards themselves will take about 1200
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November 6, 2013 1:53:43 PM

Then I don't understand your qualms about getting a 1500W supply...

Are you overclocking the cards? If not, then they shouldn't be pulling 200W, closer to that 138W value. You have to judge for yourself if you want to play it safe and get a larger power supply, or risk burning one out by getting the minimum.
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November 6, 2013 2:47:18 PM

I did not see you had 6(I thought you had just planned to use 2 of them), my bad.

Have you looked at the asic miners? they do more work per watt.
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November 7, 2013 8:09:00 AM

nukemaster said:
I did not see you had 6(I thought you had just planned to use 2 of them), my bad.

Have you looked at the asic miners? they do more work per watt.


scryptcoins are mostprofitable asics mine a sha256 coin called bitcoin
What if I use more than 10 psus to minimize price???I want to power 6 graphics cards
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November 7, 2013 8:12:24 AM

I would not go with a bunch of lower end power supplies.

If you had to go 2 I could see it(for your 6 card system), but 10+ would lead me to guess they are all cheap and unreliable(if the price is too good to be true, it is for a reason when it comes to power supplies.).

As more people get into bitcoin mining, the profit goes down(it cost more to get more than it did in the start).
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November 7, 2013 8:14:27 AM

nukemaster said:
I would not go with a bunch of lower end power supplies.

If you had to go 2 I could see it(for your 6 card system), but 10+ would lead me to guess they are all cheap and unreliable(if the price is too good to be true, it is for a reason when it comes to power supplies.).

As more people get into bitcoin mining, the profit goes down.


Thx 4 ur quik answer
How do I know if the cheap PSu is too low quality to buy it?
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November 7, 2013 8:18:14 AM

Check the 12 volt rail ratings.

You will see many cheap "500-600" watt units that have less power than a quality 300-400 watt unit.

Also look for a power supply that is rated at high temperatures since power output drops as temperatures go up.

The 120/240 or 110/220 switch is also an indicator of an older power supply(while some are still good units) unit. All the 80+ units should be newer designs with more power on the 12 volt rail compared to the older designs that did not place that much power on the 12 volt rail.
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