Corsair 750W Enough To Crossfire Or SLI?

[happy]

Hi,
So I couldn't pass up a 750 corsair I just bought. So now the question is will it be able to power this:
CPU: i7-2600
GPU: x2 7970, or 6970, or 680
HDD: x2 1TB HDD
Fans: x3 80mm fans
RAM: 8GB 1600mhz

Just wanted to get opinions if anybody is running this type of setup.

Thanks

[DOM]

I'm going to say yes but not if your going to oc with 2 cards

[Crap Daddy]

For the 680 is OK even if you OC in the limits NV set for the card. For the 7970s you will be able probably to do a mild OC. The 6970s consume more so OC will be limited. But at everything stock it's no problem.

[happy]

Originally Posted by DOM

I'm going to say yes but not if your going to oc with 2 cards

Nope, no OC for me. Just like to have everything at stock. I've read reviews saying that sli'ing the 680 with a 750w PSU is more than enough, but the 7970 needs a bit more power.

Thanks, just wanted to have some opinions before I get the PSU and plug the GPUs in.

[Shurakai]

Total system load from reviews seem to put two 680's in SLI at around 498w, overclocked I'd say 550-600, so 750 would be perfect.

[xBruce88x]

what model specifically is the corsair unit?

according to HW compare, the max wattage (TDP) for the cards are:

GTX680 195w (390w in SLI)
HD7970 250w (500w in XFire) ... I think this one is wrong though, I'm gonna guess 210w each and 420 total for xfire.
HD6970 250w (500w in XFire)

Your i7 is rated at 95w.

This is not to say that they can't exceed that power usage, esp if
they're overclocked any. Your best option would be the 680s in SLI.
would be about a 100w/8.3amp savings (assuming TDP)

Another thing to consider would be the amps on the 12v rail, since that's what powers the GPUs.

This is all a rough estimation and assuming the parts don't exceed TDP
and no overclocking.

Here's the stuff plugged into a power supply calculator online.

680s


7970s


6970s, ignore what i said about hwcompare i think they were off a little lol


to sum it up, I think it'd be safter to go with the 680s, though you could do it with the 7970s. No way for the 6970s though. I'm guessing the calcualtions on the site account for PSU efficiency. these are based on worst case as far as the system being at 100% usage (though not 24/7) and capacitor aging set at 20%, I guess you intend to keep the PSU for a little while since you just bought it?

[okidna]

Originally Posted by xBruce88x

Another thing to consider would be efficiency of the PSU, lets assume
80%. 80% of 750 would be about 600w, minus the 485w or so for GPUs and
CPU, leaving 115w for the rest, which should be enough. BTW, 485w
would be about 41amps for the 12v rail.

Wait a minute. It's not like that..

Efficiency IS NOT the ratio between real power and rated power.
Efficiency IS the ratio between the useful output of an energy conversion device (DC) and the input (AC).

So, if you have true power 750W PSU with 80% efficiency, you can use all the 750W to power your PC and you need 937.5 W input from AC socket (750/937.5 *100% = 80%).

If your PC need 450W, then the same PSU will need 562.5 W from AC socket (450/562.5 * 100% = 80%).

The higher the efficiency, the less input power (AC) needed and the less power turned into heat (hence, the PSU will run cooler).

Sorry for my bad english, but I hope you understand what I'm trying to explain.

[theonedub]

^ Correct. A legit PSU will produce its rated output- the efficiency just lets you know how much power form the wall it will take to get you there.

[FreedomEclipse]

Heres some good advice....

Before you SLI/CF anything think about getting a new case.....

A case that supports at least 4-6 120mm or 140mm fans. otherwise you'll probably be able to bake cakes and smelt metals with that PC when you put 2 hi-end graphic cards in there.

as for the PSU question... Its a hard decision as youre not overclocking, but i wouldnt risk it.



Legit reviews says 6970 in CF eats at least 596w, that leaves 154w left for other things.
Even though it might work with an exceptionally good PSU - e.g. Corsair AX750 Pro Gold series.
you will be pushing that PSU to the brink of what i would call its safely capable of and when you do that, the lifespan of the PSU becomes a short one as you are literally stressing the PSU despite it being rated for that wattage

7970 CF is probably a better and safer option....


as it only draws 407w.

though with no overclocking, your CPU becomes the graphic cards limiting factor. your 2600 might not bottleneck the cards but it will hold them back from their full potential

[okidna]

Originally Posted by FreedomEclipse

Heres some good advice....

Before you SLI/CF anything think about getting a new case.....

A case that supports at least 4-6 120mm or 140mm fans. otherwise you'll probably be able to bake cakes and smelt metals with that PC when you put 2 hi-end graphic cards in there.

as for the PSU question... Its a hard decision as youre not overclocking, but i wouldnt risk it.

http://www.legitreviews.com/images/r...onsumption.jpg

Legit reviews says 6970 in CF eats at least 596w, that leaves 154w left for other things.
Even though it might work with an exceptionally good PSU - e.g. Corsair AX750 Pro Gold series.
you will be pushing that PSU to the brink of what i would call its safely capable of and when you do that, the lifespan of the PSU becomes a short one as you are literally stressing the PSU despite it being rated for that wattage

7970 CF is probably a better and safer option....
http://www.guru3d.com/imageview.php?image=35462

as it only draws 407w.

Keep in mind that those LegitReviews power consumption is TOTAL system power consumption while Guru3D is CARD only power consumption.

[FreedomEclipse]

Originally Posted by okidna

Keep in mind that those LegitReviews power consumption is TOTAL system power consumption while Guru3D is CARD only power consumption.

well in that case a 7970CF is probably out of the question too.

[xBruce88x]

Originally Posted by okidna

Wait a minute. It's not like that..

Efficiency IS NOT the ratio between real power and rated power.
Efficiency IS the ratio between the useful output of an energy conversion device (DC) and the input (AC).

So, if you have true power 750W PSU with 80% efficiency, you can use all the 750W to power your PC and you need 937.5 W input from AC socket (750/937.5 *100% = 80%).

If your PC need 450W, then the same PSU will need 562.5 W from AC socket (450/562.5 * 100% = 80%).

The higher the efficiency, the less input power (AC) needed and the less power turned into heat (hence, the PSU will run cooler).

Sorry for my bad english, but I hope you understand what I'm trying to explain.

my bad... was really tired... i gotta remember not to think so much when i'm half asleep lol. I was thinking of capacitor aging to be honest. I edited the post to clear up any confusions lol.

[happy]

Thanks for the help guys, I used that calculator but sometimes its off. Oh and the 750w is a HX model.

Edit: Was hoping to crossfire to grab a 7970 and crossfire it in the future. I would get the 680, but I think more vram would benefit in the future. Thanks

[xBruce88x]

One last comment on gpu choices, you may want to look at the new AA/AF nvidia has with the 680.

http://www.techpowerup.com/reviews/N...GTX_680/2.html


Also, I've seen 4GB versions. (soon to be released anyway)

[Phusius]

Bruce, that does not seem very accurate. Also, I imagine quality of 8x MSAA would depend on the game itself. At 1440p and 8x MSAA I notice no jaggies at all. There comes a point when TXAA is really just a gimmick. Maybe not for 1080p, but for 1440p it is just a gimmick to me.

[xBruce88x]

Its not so much the quality but the fact that its very close/a little better than MSAA 8x with about the performance impact of MSAA2x, Then there's TXAA2 which is far better than MSAA8x with the performance impact of MSAA4x, meaning you can apply a higher filtering setting with more FPS

then there's adaptive vsync

also there's more to it than just res... some people game on large TVs rather than monitors. And 1080p at 40+in the jaggies get noticeable lol

[happy]

Originally Posted by xBruce88x

One last comment on gpu choices, you may want to look at the new AA/AF nvidia has with the 680.

http://www.techpowerup.com/reviews/N...GTX_680/2.html
http://www.techpowerup.com/reviews/N...ages/txaa2.jpg

Also, I've seen 4GB versions. (soon to be released anyway)

Hey thanks man for the suggestion, but I couldn't wait any longer. I got a 7950 maybe even crossfire it in the future. I think the Corsair 750w will be able to handle it this time. Now I'm hoping the new nVidias will do poorly.