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Corsair 650TX PSU work with dual Radeon 4870 1GB 256-bit GDDR5?

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April 17, 2009 5:08:20 PM

I am building my first PC. As of yet, I have:

Antec 900 Case:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Corsair 650W Power Supply:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Intel Core i7 920 Nehalem 2.66GHz 4 x 256KB L2 Cache 8MB L3 Cache LGA 1366 130W Quad-Core:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

XIGMATEK Dark Knight-S1283V 120mm Long Life Bearing CPU Cooler (not going with the stock cooler):
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Still deciding on RAM, Motherboard, Hard Drive and Video Card, which will be bought early next week.

I am liking the ATI Radeon 4870 1GB 256-bit GDDR5 card and am wondering if two of these can be used with the Corsair 650TX 650W PSU... this building is new to me and want to make sure it can support two cards... I see there is only 2 x 6+2Pin and one card will need both 6pin? Is there an adapter or alternate way of connecting two video cards to this PSU?

It will likely have two hard drives (750GB Maxtors a friend is giving me, not sure of model yet) and two optical drives.

I'm hoping I don't need to upgrade the PSU to the 750W version.

Any feedback would be much appreciated.




a b ) Power supply
April 17, 2009 5:46:30 PM

The power supply is one of the most important items in a build. Go right for the card with the 4 pci-e connections. No hassle trying to get the 2 cards to work and worry about coming up short when trying to hook up accessories.

You already know you want to get 2 cards, why sell yourself short. When building for myself I learned long ago to "go over the limit" as to what I think "will be good enough" for the system I'm putting together. No regrets.

April 17, 2009 5:57:56 PM

I only thought about doing the two card setup today as I found them to be cheaper than I thought they would be. Thus my question if the Corsair 650W (which I already have at my house, having bought last week not knowing I was going to be considering a two card setup ) will have the appropiate amount of connecters to support two ATI Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 (http://www.newegg.com/Product/Product.aspx?Item=N82E168...)

Can I hook two of these cards up to the Corsair 650TX?
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April 17, 2009 6:05:43 PM

And BTW - the 650TX will have plenty power - you just need some 6 pin adapters
April 17, 2009 6:11:45 PM

Wow. I'm not worried about having enough power. I am unsure about the physical connection from PSU to Video card. I know I can hook up one, is there enough connectors to do two cards. I am unsure if there are adapters if there is not... I've stated this is my first time building a PC. I don't know all little details and was hoping someone could have a simple yes or no answer. If no I know I have to return the 650TX for the 750TX.
a c 140 ) Power supply
April 17, 2009 7:54:26 PM

As a simple rule of thumb, if a psu has enough connectors for the vga cards, it will run fine. If not, be careful.
Vga cards come with molex to pci-e connectors so attaching two units should not be a problem.
Quality units such as corsair can be expected to deliver their advertised power, and even more at peak.

That said, a psu operates most efficiently in the middle third of it's power range. You will save electricity, and be quieter with a properly sized psu.
If you are planning on sli/crossfire, consider a 750w unit with 4 pci-e connectors.
A 750w unit from corsair or PC P&C will be $110.

As an alternative look at a single card like a 4870X2.
a c 248 ) Power supply
April 17, 2009 8:33:59 PM

geofelt - we've had a couple of similar threads where the efficiency of psu's was mentioned. Don't know if you saw them. The Corsair power supplies are over 80% efficient anywhere from 20% to 100% of load capacity. The best ones peak at 87% efficiency around 60% to 75% of load capacity.

If you go to the Corsair web site and look around you can find the efficiency charts and see for yourself. I was skeptical so I went over to JonnyGuru.com and a couple of other web sites that do technical reviews and testing. They verified Corsair's claimed efficiency range.

Two 4870 video cards operating in Crossfire mode will draw about 300 watts and 25 amps at full load. The source of the information is a graphics card article about how much power video cards actually use that was published last January right here at THG. A high end power pc with overclocking and typical components would require about another 250 watts. That would put power requirements right around 550 watts or so at full load. A diffrent web site measured about 500 watts during a gaming session.

That places the Corsair TX650 right in the "sweet spot".
a b ) Power supply
April 18, 2009 1:53:04 AM

JohnnyLucky said:

If you go to the Corsair web site and look around you can find the efficiency charts and see for yourself.


All the efficiency graphs at Corsair show best efficiency between 40-70%, with the peak at 50%.
April 18, 2009 2:09:40 AM

Get OCZ Gold RAM and a 4870 x2 instead of 2 4870's in Crossfire. Even if both cards run at x16 you won't get the same performance as you would with an x2 card. And if you get the 4870 x2 you could even add a 4870 into the extra slot later for even more performance.
a c 248 ) Power supply
April 18, 2009 4:01:49 AM

theAnimal - Yes, you are correct most of them peak lower but they got one that JonnyGuru.com said peaked at a higher load and maintained the peak longer. They were quite impressed with the model. I am growing old disgracefully and I do get things mixed up. I'm not exactly relishing the thought of going back and reading every bloody Corsair review. It's probably going to be the last one I read.

In the meantime, I have been giving psu efficiency some thought. I think I am beginning to see a trend in efficiency and recommendations. I'm thinking rather than continue here we probably should start a brand new thread.

EDIT - Give me a couple of days to gather my thoughts and do a little research before I start a new thread about psu efficiency.
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