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How much power do these graphics cards use?

Last response: in Graphics & Displays
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February 21, 2013 1:58:14 PM

Hey everyone.

I'm about to get two Radeon HD 3870X2 graphics cards (for a total of 4 GPU's on two PCB's.)

How big of a power supply will I need to power two Radeon HD 3870X2 dual-GPU graphics cards in quad-CrossFire?

I currently have an OCZ ZS-Series 650W 80 PLUS Bronze power supply in my system. Will this be enough, or will I need a bigger power supply? How much power do two HD 3870X2 graphics cards use together?

**Please don't give me a speech about how old the HD 3870X2 is. I know how old of a card it is. I just simply want to know how much power both will consume, and how big of a power supply I'll need to power both cards.**

More about : power graphics cards

a c 92 ) Power supply
a c 176 U Graphics card
February 21, 2013 2:08:13 PM

Why in the heck would you even bother? If you know the speech then why do it anyways?

190W each so around 380W-400W load. Assuming a normal 95W quad core CPU and a system would be around 550W. Your PSU should just cover it assuming you have enough PCIe plugs. But again, don't even bother.
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February 21, 2013 2:27:05 PM

4745454b said:
Why in the heck would you even bother? If you know the speech then why do it anyways?

190W each so around 380W-400W load. Assuming a normal 95W quad core CPU and a system would be around 550W. Your PSU should just cover it assuming you have enough PCIe plugs. But again, don't even bother.


I have an AMD Phenom II X4 965 Black Edition 3.4GHz quad-core 125W CPU + 4GB of G.SKILL DDR3 1333MHz RAM + two 120mm fans + two hard drives + an Arctic Cooling Freezer XTREME Rev.2 aftermarket CPU cooler + case lights.

Don't know if that helps or not with determining if my 650W OCZ-ZS Series 80 PLUS Bronze power supply will be able to power both cards plus all of the other parts in my computer, but... there you go.
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a b ) Power supply
a b U Graphics card
February 21, 2013 2:27:52 PM

I must echo 4745454b ... your desire for no one to comment on the fact that you're looking at getting two 3870x2 cards is a real head scratcher. Unless you're getting them for less than $50 a pop, what's the point.

Also, if I am not mistaken your current power supply only has 2 PCIe cables, 1 6 pin and 1 6+2 pin. If I looked at the images for the 3850x2 correctly, you will need two plugs PER card, leaving you two short. Yes, you can technically use the molex to PCIe adapter included with most cards ... but it isn't recommended.
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February 21, 2013 2:30:42 PM

Spaniard United said:
I must echo 4745454b ... your desire for no one to comment on the fact that you're looking at getting two 3870x2 cards is a real head scratcher. Unless you're getting them for less than $50 a pop, what's the point.

Also, if I am not mistaken your current power supply only has 2 PCIe cables, 1 6 pin and 1 6+2 pin. If I looked at the images for the 3850x2 correctly, you will need two plugs PER card, leaving you two short. Yes, you can technically use the molex to PCIe adapter included with most cards ... but it isn't recommended.


Why isn't it recommended?
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a b ) Power supply
a b U Graphics card
February 21, 2013 2:31:23 PM

Not as stable as dedicated PCIe plugs.
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February 21, 2013 2:33:06 PM

firinmylazerman said:
Why isn't it recommended?


Because newer technology at $70 is better than older technology at $70 (generally speaking of course). You could probably get a card with similar performance at the same price with DX11.
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a c 92 ) Power supply
a c 176 U Graphics card
February 21, 2013 3:10:54 PM

I'm not even sure $50 each is a good deal. Memory says 3870 is around the performance of the 4870 give or take. And quadfire scales HORRIBLY. Evens out the frame rates but doesn't add much to the total package. If you figure 400W of GPU power for similar performance to a 6850/70(?) it doesn't seem like a good idea. And at ~$100 I'm not sure you'd be saving much money. More so when you consider how much power you'll be wasting compared to other cards. A 7850 is around $150, and only uses around 130W and I'd bet its close to 3870 QF.
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a b ) Power supply
a b U Graphics card
February 21, 2013 3:24:34 PM

I don't think anyone aside from OP will argue that the two 3870x2 cards doesn't make sense. To answer the OP's question though, the PSU should have sufficient power, but not sufficient PCIe cables.

If I am looking at the right one, you only have one cable molex with 4 connectors. This is not even enough to use the adapters. In order for the connection to be stable, the Molex to PCIe adapter should be attached to different molex cables/line. Basically, using two adapters, you should have those two adapters connected to 4 different cables and one adapter per card.

See the problem? You are going to have to buy a new PSU if you insist on going with the 2 3870x2.
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February 21, 2013 3:58:51 PM

Don't listen to them, OP, just do it and see what happens -- the experiment would be well worth the $200. Be the first one on your block to QuadFire. The OP wants to do something he _can_ do, but not necessarily what he _should_ do -- and I support this sort of thinking.
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March 27, 2013 2:38:40 PM

Quadfire won't work.:no: 
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