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Will 750w be enough?

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  • Components
  • MSI
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August 19, 2014 11:34:38 AM

I want to purchase 2 MSI Radeon R9 280X Gaming 3G Twin Frozr IV OC GPUs running in crossfire. Running with an intel i5 4670k. 8GB of G skill ram on a gigabyte z97 g55 motherboard. Will 750w be enough? If so.. what psu would you recommend?

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August 19, 2014 11:42:46 AM

The corsair AX-860 is a good choice, or you could buy a 760 Watt SeaSonic PSU.
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August 19, 2014 12:01:46 PM

cjrw59 said:
I want to purchase 2 MSI Radeon R9 280X Gaming 3G Twin Frozr IV OC GPUs running in crossfire. Running with an intel i5 4670k. 8GB of G skill ram on a gigabyte z97 g55 motherboard. Will 750w be enough? If so.. what psu would you recommend?


Based upon your setup, I think an 850w PSU should do the trick.

Check out this website: http://extreme.outervision.com/PSUEngine

I ran the calculations for you based upon your setup with a few assumptions:
1) You have a "k" CPU, so I assume you are overclocking it. I have assumed you've bumped it up to 3.7GHz;
2) I have assumed you are running 1 SSD and 1HDD, 1DVD-R/W drive;
3) You have four case fans; and
4) You are running four USB devices (i.e. mouse, camera, keyboard, etc.).

My calculations may differ from reality, as you will have to make adjustments yourself based upon your rig. However, I believe that we're accounting for the big ticket (wattage-wise anyways) items, so this should be representative of your setup.

Using this calculator, your wattage came out to 673 Watts.

Why not a 750W PSU then, you ask? Well, I abide by the 15% rule when using these calculators: Whatever this gives you, add another 15% on top. This is because a lot of people with Hawaii-based cards like ours (I am running 2xR9 290s in Crossfire on a Corsair AX860i PSU) tend to have fairly substantial power fluctuations under load. So, if you buy a 750W PSU, your headroom is approximately 11.5%. Buying an 850W PSU will beef that up to a healthy 26% overhead.

Might seem like overkill to you, but I upgraded due to system stability from a 750W PSU and ever since, my stability issue has gone away.

Happy hunting!
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