Oh look, another noob asking if he needs x amount of watts for SLI/Crossfire

[parablooper]

So, I have an HX650. Nice modular Corsair PSU, +12V @54amps, and 80+ gold certified, 90% efficiency under load.

I have an FX-6300 at a moderate overclock (I always fear that I will "burn out" the CPU for some reason, also it keeps the fan nice and quiet) of 4.2Ghz @ 1.4125V.

My Sapphire 7870 XT graphics card is on stock voltage, overclocked to 1100MHz, 1600MHz memory, with a +7 board power draw (Trixx utility, I dunno exactly how it works). I'm not sure of the voltage, but according to a random bitcoin thing I was looking at it was 1.256V.

I plan to buy another one of those GPUs^.

Will the 650W be enough?

Would turning down the GPU OC help lower their power draw? I'm willing to lower some of their speeds since having two of them will no doubt bring me up to 60+ FPS on basically all games (I mean, with exceptions, like Witcher 2 ubersampling or unigine heaven).

My other question is, how can you tell when your power supply is not providing sufficient wattage? Will you get random shutdowns/bluescreens? CPU/GPU throttling? Is there any software to help you see where your power is going, and how much?

 

[AMD64Blondie]

http://www.amazon.com/PC-Power-Cooli...urbo-cool+1200

You're welcome.

Sorry,I'm biased as I own one of these $450 wonders. Also have a 7-year-old Turbo-Cool 510 SLI in my backup Linux PC,still running flawlessly.

 

[fffblackmage]

My other question is, how can you tell when your power supply is not providing sufficient wattage? Will you get random shutdowns/bluescreens? CPU/GPU throttling? Is there any software to help you see where your power is going, and how much?

BSOD or random shutdowns sounds right, though I've never experienced a problem with insufficient power. CPU/GPU throttling occurs when they're running too hot, not because of power issues.

I'm not aware of any software that can really give you accurate power readings, but the easiest way I can think of is just getting yourself a Kill-A-Watt meter. That'll give you the power draw of your entire computer at the wall. Just remember that the PSU is not 100% efficient, so some power is lost through waste heat. For example, if your computer is using 500W at the wall, and your PSU is 80% efficient, then the PSU's actual power output is 400W.

I think 650W is enough as long as you have a good PSU (Corsair HX650 is good). Most people probably like to have more headroom though. I usually have a rough idea of how much power my computer uses with the Kill-A-Watt meter, and I know I'm not even maxing out my PSU's 500W power output even if I do silly things (insane and unsafe overclocking and overvolting).

 

[parablooper]

Ok

 

[biostud]

Yes you have enough power to run your system with 7870 in CF.

 

[parablooper]

Well, big blunder on my part. HX650 is "SLI ready" but not "CrossFire ready." It only has 2 PCI 6+2 connectors, and I need 4. Gotta cough up more money now.

 

[Accord99]

Well, big blunder on my part. HX650 is "SLI ready" but not "CrossFire ready." It only has 2 PCI 6+2 connectors, and I need 4. Gotta cough up more money now.

It should have plenty of molex connectors though and the video cards should come with molex-to-pci-e power adapters .

 

[parablooper]

It should have plenty of molex connectors though and the video cards should come with molex-to-pci-e power adapters .

So I can convert the SATA/peripheral output into PCI power with the appropriate adapters? Because that would be really great.

 

[TemjinGold]

So I can convert the SATA/peripheral output into PCI power with the appropriate adapters? Because that would be really great.

Yes.

 

[parablooper]

Okay, I found two molex-to-PCI converters from the video card... but only one actual PSU-to-molex. But that one connector splits into two molex outputs. Would that work? Can one 6-pin connection into the PSU cover both of the 6-pin PCIs on the graphics card?

...or is that just silly?

 

[Accord99]

I thought the HX650 Gold has 2 cables with 4 molex connectors each?

http://www.newegg.ca/Product/Product...82E16817139012
http://www.hardwaresecrets.com/fullimage.php?image=52170

If you can find both, I would connect one PCI-e cable from the PSU to each card, then one adapted molex to PCI-e power to each card.

Another option is to use a PCI-e power splitter:

http://www.newegg.com/Product/Produc...82E16812201038

 

[chimaxi83]

http://www.amazon.com/PC-Power-Cooli...urbo-cool+1200

You're welcome.

Sorry,I'm biased as I own one of these $450 wonders. Also have a 7-year-old Turbo-Cool 510 SLI in my backup Linux PC,still running flawlessly.

Do you have any idea what this thread is about?

Well, big blunder on my part. HX650 is "SLI ready" but not "CrossFire ready." It only has 2 PCI 6+2 connectors, and I need 4. Gotta cough up more money now.

SLI ready is the same as crossfire ready. Do what others have suggested and convert some of your connectors. Your PSU is good for the setup you want to have.

As for power monitoring, the best in my opinion is a Kill-a-watt meter. Beyond that, I use HWiNFO64 software as a rough estimate.

 

[parablooper]

Sweet. Turns out one of my molex cables was already IN the power supply, connected to the front LED fan (I think...). Just as a test, I powered down, and put two molex-to-PCIs into my current single graphics card. I am writing with that setup right now, and it seems to be working.

Now I have the two dedicated 6-pin PCIs free for when I get the second card.

Thanks everyone.