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If I want 2 GPUs, what do I look for in a new PSU?

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Posted

Let's assume I wanted to buy a new PSU so that I can run two GPUs (SLI/CFX).

 

What am I looking for when it comes to a PSU? What part of the description am I looking at?

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You basically want a 700W+ PSU from a reputable manufacturer that specifically mentions SLI / Crossfire, as that will have adequate rails to handle multiple GPUs. An example of that would be the Cooler Master GX 750W. Just make sure whatever you're looking at has a high efficiency rating (i.e. 85%+) especially if you're combining it with an overclocked system. There are plenty of online tools to calculate your power load by inputting your components, which should give you a ballpark figure of the needed wattage.

 

Personally I opted for a 1000W modular Cooler Master, which more from comfortably handles my 4.6GHz 2600K and two overclocked GTX680s in SLI.

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Posted

That it supports SLI/XFire (should say so in the description!), has enough PCI-E connectors for two of the specific cards you're looking at, that's it's a reliable unit (check reviews), that the total wattage is enough. I would say 600W is enough for mid-range cards typically, but to be comfortable get 700W+ as theyarecomingforyou said.

 

Apart from that, general qualities of all PSUs - efficiency, silence, modularity.

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Posted

Cheers muchly, guys :)

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Posted

 What part of the description am I looking at?

 

The key words are gold/platinum/plus :)

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Posted

Whatever you do don't buy cheap, as with power supply's you get what you pay for.

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The key words are gold/platinum/plus

 

Really?  So "CheapAsia RadomBrand 500w SuperGoldPlus" would do?  Obviously a made-up name but it demonstrates that words such as those you suggested mean nothing, and thus are no indicator of ability or specification.

 

Or did I miss some sarcasm somewhere?

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Posted

Buy any know brand of psu, like corsair, cm, antec etc and you should be ok. 750w and up will do the job unless you do titan sli lol

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Posted

Really?  So "CheapAsia RadomBrand 500w SuperGoldPlus" would do?  Obviously a made-up name but it demonstrates that words such as those you suggested mean nothing, and thus are no indicator of ability or specification.

 

Or did I miss some sarcasm somewhere?

 

It's not just a catchy word inserted in the name. It's a reference to the 80 Plus certification programme. Obviously, I only meant legit products.

 

And the point was to avoid bronze and silver class PSU.

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Posted

If we're nitpicking about efficiency, do not forget that it is a curve that often peaks at medium/medium-high loads. Therefore, care must be taken to not only keep maximum loads in mind, but also average and idle.

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Posted

But that certification doesn't represent whether it will hold up and deliver the power needed?

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Posted

Also look for a single rail PSU as there more efficient and provide better power output for duel GPU setups.

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Posted

But that certification doesn't represent whether it will hold up and deliver the power needed?

While it directly speaks only about efficiency, you'd be hard pressed to find enough turd polish to make a badly designed and cheap unit run efficient.

So it's an overall statement of reliability and stability, including rapidly changing loads and temporary overloads.

 

Also look for a single rail PSU as there more efficient and provide better power output for duel GPU setups.

Sorry, that's bogus. I've fallen for this myth myself for a long time, it's very popular. Sure, one would need to keep in mind limits of each rail, but that's about all there is to it. Rails are a design decision.

 

And while prevalent, single rail comes with its own problems. As Oklahoma Wolf has cleverly said - with a near-kilowatt unit you can arc-weld. Its single OCP trip is set a fair margin above its maximum load, enabling potentially devastating short-circuit, made possible by, for example, a defective SATA power cable - it's all too easy to damage those accidentially. Such occurence would also present a dangerous overload condition for the whole unit. Multiple rail configurations somewhat diminish that.

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Posted

Depends on the GPUs you want to run but I'd say 750W or higher.

 

There are plenty of good manufatures out there but I recommend SeaSonic and Corsair (A number of Corsair PSUs are built by SeaSonic).

 

A high 80 Plus rating (Silver, gold, platinum) isn't required but is nice as it specifies the PSU has high effiency at AC->DC which means less power used and usually less heat.

 

My PSU is 80 Plus Platinum and it doesn't even require the fan to spin if you're below 20% usage (which I am while browsing).

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Posted

While it directly speaks only about efficiency, you'd be hard pressed to find enough turd polish to make a badly designed and cheap unit run efficient.

So it's an overall statement of reliability and stability, including rapidly changing loads and temporary overloads.

 

Sorry, that's bogus. I've fallen for this myth myself for a long time, it's very popular. Sure, one would need to keep in mind limits of each rail, but that's about all there is to it. Rails are a design decision.

 

And while prevalent, single rail comes with its own problems. As Oklahoma Wolf has cleverly said - with a near-kilowatt unit you can arc-weld. Its single OCP trip is set a fair margin above its maximum load, enabling potentially devastating short-circuit, made possible by, for example, a defective SATA power cable - it's all too easy to damage those accidentially. Such occurence would also present a dangerous overload condition for the whole unit. Multiple rail configurations somewhat diminish that.

True enough, I have never had any problems with single rail PSU's... (If installed correctly). But anything above 900 watts you are probably better getting a multi rail PSU.

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