PSU for New 2011 Build

Just doing some research for my next build... quick question:

Would a 850W Seasonic or other trusted brand 80 PLUS certified power supply be sufficient for 100% sustained load with:

i7 3820, LGA 2011 quad core Sandy Bridge E, rated to 130W
2x HD 7970 3GB, MAX draw of ~270W
Run of the mill LGA 2011 mainboard, 32GB of ram (8x4GB), one SSD, and one HDD

Math works out to 670W full load for GPU/CPU, without an overclock.

I feel that 850W would run at stock clocks, but would not be able to take a good overclock.
A 1050W PSU would probably be a better fit.

Can anyone recommend a good PSU for this system and running requirements? The less expensive the better, but quality is the key. $200 is the most im looking to spend.

5 answers Last reply Best Answer
More about 2011 build
  1. i7-3820 at the stock 3.6 GHz @ 1.16 Vcore will be drawing 88 Watts at the +12V CPU power connector on the motherboard.

    Two reference clocked Radeon HD 7970 3072 MB GDDR5 in 2-way CrossFire mode will draw 375 Watts during gaming and 525 Watts when running Furmark stress testing.

    A good 850 Watt power supply with a combined +12 Volt continuous current rating of 70 Amps will handle a reference clocked CPU and both GPUs in that system configuration just fine.

    What magnitude of an overclock are you trying to achieve with the i7-3820?

    What magnitude of an overclock are you trying to achieve with the two Radeon HD 7970?
  2. The i7-3820 only draws 88 W full load? I know 130 W is TDP, but shouldn't that be used for a worst case scenario?

    I was hoping to overclock as high as I can go with the i7 3820 at 1.3v to be safe. The 7970s will be overclocked as far as possible with stock or near stock voltage, if possible.

    So will 850 watts with an 80plus rating be enough with such a modest overclock?

    And what little money saved on an i7-3820 over the more popular i7-2600k will be spent on the platform. A high end 1155 board is not much cheaper than a decent X79 2011 board. The i7 3820 may be partially locked, but I've seen others get them to at least 4.5 GHz, so I'm sure with a decent X79 2011 board, I can do the same.

    Thanks again!
  3. Best answer
    With the i7-3820 running at 4.5 GHz @ 1.27 Vcore measured a 135.6 Watt power draw on the +12V CPU power connector. That includes the power loss in the motherboard's CPU VRM power circuit.

    I would allow at least an extra 85 Watts on top of the 525 Watts when running Furmark for the two overclocked Radeon HD 7970 in 2-way CrossFire mode.

    A card like the MSI Radeon HD 7970 Lightning can draw up to 348 Watts when overclocked to 1170 MHz Core/1600 MHz Memory and running FurMark stress testing in's review of that card. In's review of that card they measured 379 Watts for that card while running FurMark and the card wasn't even overclocked. Running two cards like this in 2-way CrossFire mode is slightly less than double that.

    If you want the power supply to power the system under the worst case scenario, then you should be looking at something like the Corsair Enthusiast Series TX950 (CMPSU-950TX) or better.

    Your initial post suggesting a 1050 Watt may very well be the better fit.
  4. $50 more from 850w to 1050w is worth it then.

    Thank you!
  5. Best answer selected by TdiT.
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