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HD 6850 Crossfire power consumption question

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September 25, 2011 12:37:52 AM

Im just wondering ; I have got an Radeon HD 6850 with Intel 2500k 4.6ghz overlock, 1 hdd and dvd reader, one ram stick on a 600w PSU.

Is it possible for me to buy another 6850 to run in crossfire or does my 600w PSU put a stop to that?
September 25, 2011 12:51:12 AM

Not safely ;
Guru3D's power supply recommendation:

Radeon HD 6850 x1
On your average system the card requires you to have a 450 Watt power supply unit.

Radeon HD 6850 x2
A second card requires you to add another ~130 Watts. You need a 650 Watt power supply unit.
September 25, 2011 12:51:56 AM

Makke said:
Im just wondering ; I have got an Radeon HD 6850 with Intel 2500k 4.6ghz overlock, 1 hdd and dvd reader, one ram stick on a 600w PSU.

Is it possible for me to buy another 6850 to run in crossfire or does my 600w PSU put a stop to that?

A 600W PSU will be enough. Last time I checked 6850s in XFire draw from 300W to 400W. With that OC, your system will probably pull more though.
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September 25, 2011 9:05:56 AM

I WANT to think that it will be enough, can't really afford both a new PSU and an 6850.

I did some calculating on http://www.thermaltake.outervision.com/Power, and in load my system will draw 434 watts of power. I may have calculated wrong buy i re-did it three times and got approx the same watts every time 434-450 ish~.

I mean, with 150w left over there shouldn't be any problem what-so-ever, right?
September 25, 2011 10:06:58 AM

First, what 600W PSU?
September 25, 2011 12:56:39 PM

Possible I suppose. GTX480 has a TDP of 250W I believe. Round it up to 300 for the board drives and ram. Add in 100W for your normal quad and your looking at 400W for a system. As long as that 430W can do all/most of its power on the 12V rail like most new units can, you can just barely get away with this.

At the same time I can point out several units (Most diablotek units???) that are 500W or more that I wouldn't trust to power a GTX480.
September 25, 2011 1:52:29 PM

4745454b said:
First, what 600W PSU?


Corsiar CX600w, i think it has 80+ certification but i'm not sure. I calculated the load power consumption (Load=~90%) to be around 434w, and on the 4 reviews I've looked at the power consumption was from 385w - ~460w. With a 600w PSU there will be 166w over, and that's like.. Totally safe? Sounds safe to me but I'd love to hear your opinions!
September 25, 2011 2:25:50 PM

TDP for the 6850 is 130. x2 = 260 just for the GPUs. Not sure how much you've upped the voltage on your OC'd CPU, so lets say 150W just to be safe. Toss in another 50W for the board, ram, drives, etc and your at 460W.

The CX600 (either version) has 40A on its 12V rail. This comes out to 480W. This is REALLY close to what your PSU can do. You could get away with it, but you'll be putting a lot of pressure on your PSU. I vote do it, but the next upgrade you do is the PSU. Do your best to keep it cool in the mean time, and perhaps dial the CPU OC down as well. No matter what, DO NOT OC the GPUs!
September 25, 2011 3:09:15 PM

4745454b said:
TDP for the 6850 is 130. x2 = 260 just for the GPUs. Not sure how much you've upped the voltage on your OC'd CPU, so lets say 150W just to be safe. Toss in another 50W for the board, ram, drives, etc and your at 460W.

The CX600 (either version) has 40A on its 12V rail. This comes out to 480W. This is REALLY close to what your PSU can do. You could get away with it, but you'll be putting a lot of pressure on your PSU. I vote do it, but the next upgrade you do is the PSU. Do your best to keep it cool in the mean time, and perhaps dial the CPU OC down as well. No matter what, DO NOT OC the GPUs!


The overclocked CPU is at 1.35v core so 130w there. So accodring to your calculations it will be, as I've already mentioned, 440w. I had no idea it could only deliver 480w :s. So i got 40 watts over, is it safe? I will not push anything else in, i might even remove a fan if necessarily. Dont think it will make much of a difference but still, i'm willing to do it. Whatcha guys think?
September 25, 2011 9:38:23 PM

Any more thoughts?
September 25, 2011 11:17:57 PM

Makke said:
I WANT to think that it will be enough, can't really afford both a new PSU and an 6850.

I did some calculating on http://www.thermaltake.outervision.com/Power, and in load my system will draw 434 watts of power. I may have calculated wrong buy i re-did it three times and got approx the same watts every time 434-450 ish~.

I mean, with 150w left over there shouldn't be any problem what-so-ever, right?

Your PSU actually has 480w on the +12v rail as 4745454b said and that is what matters. The PSU calculators tend to overdo things a bit and you are unlikely to actually ever reach the number it gives you. So it should work but you are pushing the PSU up near its limit. Replacing it with a better PSU at some point would be a good idea, especially if you want to overclock.
September 26, 2011 4:17:00 AM

iam2, just because some guys on a forum say its overrated doesn't mean it is. No body provided any links to anywhere I trust that says its the case. The big "problem" with the CX series is unlike the previous gen they aren't as powerful on the 12v rail. The CX500 has as much power as the VX450. (33 or 34 amps for both.) If the CX was to be an improvement it should be able to handle more.

The CX is what I consider to the be Antec's "basiq" line. A cheap PSU from Corsair that can get the job done. Doesn't have tons of power, isn't the most efficient, but using it won't cause your system to blow up.
September 26, 2011 9:54:55 AM

What I will do is to buy another 6850 and after a time get a new PSU. After everything I've read here I think that it is safe. I will remove the overclock on my CPU and maybe use the "Power saving" mode on my p67 MB, if that would save me some Watts. What's the worst thing that can happen if my PSU cant handle it? Will it like, send a bolt of electricity trough my system that blows out everything? (In all seriousness, what can I expect if the PSU can't handle it?)
September 26, 2011 10:11:59 AM

Random shut downs when you draw more then your PSU can output. You shouldn't see any voltage spikes, though you could have some out of spec ripple depending on the unit.
September 26, 2011 10:12:48 AM

If your PSU can't handle it the system either won't start up or will become unstable, shutting down unexpectedly when it needs more power than the PSU can deliver, most likely during gaming.
September 26, 2011 2:56:50 PM

Yeah, random might have been the wrong word...
September 26, 2011 9:18:47 PM

But according to my calculations I have 40w over, maybe even a little more if I remove the overclocks and lower fan speeds etc. Will my system be unstable anyways?
September 26, 2011 9:25:07 PM

Probably not. I refuse to say no because dud units exist. You'll be fine, but over time as your unit is stressed you'll have issues. Run it, but upgrade your PSU when you get the chance.
September 27, 2011 3:54:22 PM

4745454b said:
Probably not. I refuse to say no because dud units exist. You'll be fine, but over time as your unit is stressed you'll have issues. Run it, but upgrade your PSU when you get the chance.


Will do, thanks everyone for the great answers!
February 11, 2012 4:29:06 PM

This topic has been closed by Mousemonkey
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