6850 crossfire

[Djentleman]

Do you guys think this power supply could run two 6850's.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341016

 

[rolli59]

It is on the low end but according to this it can http://www.anandtech.com/show/4061/amds-radeon-hd-6970-radeon-hd-6950/24 Total system load 423watts running Furmark.

 

[corroded]

could not see the newegg link :-( Like the link to stats.

I run an 6850, single. I've got the Silverstone 850 silent PSU. nice and quiet.

 

[clutchc]

Do you guys think this power supply could run two 6850's.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341016

The wattage is sufficient, but the split rails are only 18A each. 18 amps is probably enough for a maxed out HD 6850 if you can be sure nothing else is on the same rail. Some PSUs have a switch that allows you to combine the rails. If not, I would suggest a similar sized PSU with single rail. I have 2 HD 6850s in Crossfire powered by a single rail 850W XFX PSU for comparison.

 

[x Heavy]

I got a big 750 watt corsair pushing dozens of amps on one rail feeding two in cf. Going on two years service without issue.

 

[iam2thecrowe]

The wattage is sufficient, but the split rails are only 18A each. 18 amps is probably enough for a maxed out HD 6850 if you can be sure nothing else is on the same rail. Some PSUs have a switch that allows you to combine the rails. If not, I would suggest a similar sized PSU with single rail. I have 2 HD 6850s in Crossfire powered by a single rail 850W XFX PSU for comparison.

18A at 12v is 216w, add to that the motherboard supplies the card with 75 watts, thats 291w available for a pcie card. So i think thats PLENTY considering the tdp for a 6850 is 127w...people who think single rail psu's are the only way to go dont know what they are on about.
beside that, no, dont use a 500w psu for two of these, it will work but you will be making the psu run at its upper limits which is not good and the psu wont last long. opt for 600w +

 

[clutchc]

18A at 12v is 216w, add to that the motherboard supplies the card with 75 watts, thats 291w available for a pcie card. So i think thats PLENTY considering the tdp for a 6850 is 127w...people who suggest single rail psu's only dont know what they are on about.

That's very true, but the 75W that the slot provides could still be coming from the same 18A +12V rail along with the current draw from other +12V components. Although I agree, I'm probably being overly cautious. I'm just skeptical of some manufacturer's ratings...

 

[Djentleman]

I think i'm just going to try it. And if it doesn't work then; What's the worst that can happen? Could it blow up my cards lol

 

[clutchc]

I think i'm just going to try it. And if it doesn't work then; What's the worst that can happen? Could it blow up my cards lol

It won't "blow up your cards". If the PSU can't handle the load, it will just shut down. Or cause a re-boot. In the real world, you'll probably be fine.

Here's a PSU calculator if you feel you need it:
http://www.extreme.outervision.com/psucalculatorlite.jsp

 

[clutchc]

18A at 12v is 216w, add to that the motherboard supplies the card with 75 watts, thats 291w available for a pcie card. So i think thats PLENTY considering the tdp for a 6850 is 127w...people who think single rail psu's are the only way to go dont know what they are on about.
beside that, no, dont use a 500w psu for two of these, it will work but you will be making the psu run at its upper limits which is not good and the psu wont last long. opt for 600w +

#1: I didn't say single rail was the only way to go. I merely suggested the single rail would be preferable... in my opinion.

#2: With 40 years of electrical experience behind me, I feel I do kinda know what I am talking about.

 

[Djentleman]

Best answer selected by djentleman.