800 watt psu sufficient for crossfire

weavenation · Oct 7, 2015

Im looking into upgrading my psu to a modular psu, mine is not. When i purchase it, i will have an i7 6700k oc'd to 4.4 or 4.5 ghz. Not any further. 16 gb ddr4 ram 2666 mhz. 2 r9 390s in crossfire. Theyre the 8 gb ones that you can almost steal from newegg right now for under 300 bucks each, they will be Oc'd as well. I have a basic lg disk drive, 128 gb ssd, 2 tb HDD. And i think 5 or 6 fans. My cpu will be cooled by a 120 mm astek liquid cooler. Im thinking 800 watts is a for sure answer, but i would definitely love to hear any other thoughts. Thanks in advanced

Oli_The_Anarchist · Oct 7, 2015

right it is not all about watts, you could buy a 1000 w unbranded PSU and It would not perform well and may not even boot however you can buy a 800w seasonic and it would probably run it quite smoothly! I think that you want to be going for a 900 to 1000 watt good quality power supply, this leaves you loads of room to overclock etc, I reckon stock your system would run 700-800w so getting a 1000 watt power supply allows for upgrades and overclocks and also a good quality one would be very stable and the system would be very nice to use!
https://pcpartpicker.com/part/xfx-power-supply-p11000belx ridiculously reliable however hefty price tag!
https://pcpartpicker.com/part/xfx-power-supply-p11250befx still very reliable, lots of power and also $30 off on newegg at the minute so it is totally up to you what you do! between them!

Darkbreeze · Oct 7, 2015

1000w is recommended.

http://www.realhardtechx.com/index_archivos/Page362.htm

If you go with a top tier unit, like any Tier 1 or 2 unit here:

http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

Then you could probably get away with an 850w unit, but you won't be doing any overclocking of the GPU card or CPU unless you opt for a 900w or higher unit of high quality.

viewtyjoe · Oct 7, 2015

I'm always one for safety. The PSU will only use what it needs to, generally, so there's little downside to going somewhat bigger than you need. I'm going to echo darkbreeze's comment above that 1000w is recommended. IIRC, 390s can pull 350-400w under full load at stock clocks, and while that is unlikely in normal sustained usage, you can see some spikes that'll kill you if your PSU can't handle it.

Darkbreeze · Oct 7, 2015

Spikes and out of spec behavior on big cards are the only reason I even recommend going with the "recommended" capacity. It can and does happen, and if you're borderline already on a "meh" unit, it's gonna start introducing incremental damage a little at a time, or in some cases instantly. Higher end units generally have good enough protections to mitigate these kinds of fluctuations, but still it's not harmful in any way to go with the recommended spec either.

weavenation · Oct 8, 2015

viewtyjoe :

so theyll each be able to pull around 400 watts each???? im sorry if i sound more than a little astounded. i had no idea the difference in power draw between the 380s and 390s was so immense. i have 2 2gb 380s in crossfire right now on a crappy 750 watt psu.

weavenation · Oct 8, 2015

Darkbreeze :

ok, so im trying to budget a psu as most/all of my money will be spent on the graphics cards. any chance this psu has a real possibility of being sustainable. http://www.newegg.com/Product/Product.aspx?Item=N82E16817182325&cm_re=photon_1000-_-17-182-325-_-Product
is that brand worth taking a chance on? most of the reviews make it seem adequate but that brand isnt well known at all

Darkbreeze · Oct 8, 2015

No, the Photon is poor quality. Actually, the brand is VERY well known, since it's Newegg's house brand. The only units Rosewill makes that I'd trust are the Capstone series units, the older ones, not the newer ones. The rest are "meh".

This unit will run those cards just fine and is a HIGH QUALITY Super Flower built unit.

PCPartPicker part list / Price breakdown by merchant

Power Supply: EVGA 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($117.99 @ NCIX US)
Total: $117.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-08 03:30 EDT-0400

weavenation · Oct 8, 2015

Darkbreeze :

ok, i put pretty much my whole final system on pcpartpicker and it showed it using 762 watts. if i dont OC the cpu and OC the gpus will 850 watts suffice? another option im thinking is not even OCing the gpus cause i have 2 2gb r9 380s and they're letting me run games at 4k at 40-70 fps on medium settings. im thinking i shouldnt even have to oc the 390s to push 4k as i want it? what do you think?

Darkbreeze · Oct 8, 2015

The R9 390x CF, which only calls for 100w more than the R9 390 CF, pulled 805w from the wall in testing.

http://www.tweaktown.com/news/45983/amd-radeon-r9-390x-cards-crossfire-use-up-800w-power-4k/index.html

If you plan to overclock the CPU or the GPU cards, I'd play it safe and go with this unit which is the least expensive quality unit above the G2 850 I listed above.

PCPartPicker part list / Price breakdown by merchant

Power Supply: SeaSonic X Series 1050W 80+ Gold Certified Fully-Modular ATX Power Supply ($143.00 @ Newegg)
Total: $143.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-08 03:42 EDT-0400

weavenation · Oct 8, 2015

thank you dark for your prompt responses. i appreciate everyones input and will be going for at least 1000 watt psu.

Darkbreeze · Oct 8, 2015

Good luck in your endeavor. Should work out fine.

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800 watt psu sufficient for crossfire

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