Crossfire power consumption

[Patoson]

I wanted to get a second 270x for Crossfire, and I read everywhere that I should have a 750W PSU, which I have, except for one thread where they said a quality 600W PSU could do.

The problem is that I recently purchased a UPS of 1000VA/600W, making the mistake of not looking at the W (and I also was convinced that my PSU was of 600W). After speaking to the shop, I cannot RMA it because the deadline is over. And, if I wanted Crossfire, most threads I've seen (tomshardware mostly) say you need 750W for Crossfire.

Then, in the same message where the shop told me I couldn't RMA, they said the manufacturer of the GPU specifies it only needs 600W for Crossfire (and it indeed says so in the page where I bought it), and it's the only guys who claim that.

If anyone has some advice I would really appreciate it. I don't know if I can go for it and use this UPS or it will end up getting fried or frying my computer.

(click to show/hide)

CPU: i5 3570-k @ 4.0GHz
RAM: 8Gb DDR3 1600 CL7
GPU: Sapphire R9 270X Dual-X 2GB GDDR5
MOBO: Asrock Z77 Extreme4
PSU: Corsair HX750

[Dalhi]

You may want to check some tests, like this one for example: http://www.tweaktown.com/articles/5984/sapphire-radeon-r9-270x-2gb-toxic-video-cards-in-crossfire/index.html

[Molly]

VA is irrelevant in this case. It's all about the Watts...

Checking the consumption of one card should give you a good clue about the drain both gonna create - it's just x2 during load, I guess. At least I wouldn't know a reason why they should take less power really. And you wanna design for max possible load anyway...

Check one card for their power demand, multiply it by 2 and there you go...

[Patoson]

But what would happen if I used more power than my UPS can handle? Would it be damaged? Or damage my computer?

[Molly]

But what would happen if I used more power than my UPS can handle? Would it be damaged? Or damage my computer?

First issue would be heat. Most modern PSU have safety electronics tho, I'd say they simply shut down before permanent damage is done. But heat can be an issue in the Summer...

My advise would probably be to make some proper google search about your specific hardware for their power intake and simply count it all together to get an overview. Right now it's basically just a guessing game.