Sign in with
Sign up | Sign in
Your question

750Watt PSU Enough?

Last response: in Components
Share
January 9, 2009 4:56:47 PM

Here is my current rig:

Q9550 @4.0 GHZ (OCed)(1.3V)
Asus P5N-D Mobo
8 Gig of Corsair dominator ram @1200 MHZ
thermaltake bigwater 760i liquid cpu cooler.
x1 samsung 22x burner
x1 veloiraptor (OS)
x1 WD black ED HDD (Data)
x1 evga GTX260 Core 216 @ 750/1600/2400 (OCed)(1.8V)
x1 750 Watt PC&Powercooling PSU with a 60A rail.


My question is this. I would like to purchase another GTX260 (and OC it just the same) and run SLI mode.

Will my PSU be enough? I wa sjust reading about how a new core I7 with quad GTX295's runs about 730 watts.

So my system should be far under that.

I really don't want to by a new PSU considering this one is 35 days old :) 

Thanks for all the help guys!

More about : 750watt psu

a b ) Power supply
January 9, 2009 5:22:35 PM

It should work, because that is in fact an 825W PSU IIRC. I'm pretty sure it wouldn't work with some other "750W" PSUs, especially since you're overclocking the CPU and the video cards. Any idea how much the liquid cooler consumes?

a b ) Power supply
January 9, 2009 5:39:23 PM

I just got a TX850W-Corsair because I thought the 750 might not be enough. Intel quad core/EVGA 750sli/8gig pc6400/2GTX260....all the usuals...... doesn't miss a beat.
Related resources
a b ) Power supply
January 9, 2009 5:48:51 PM

How is that TX850, is it quiet? I might want one too soon.
January 9, 2009 5:55:16 PM

Swifty, I got the PC&Powercooling brand because the forums all said it's the best of the best. And because of the single rail. I'm not sure if the corsair one does, all the sub $100 ones i've seen don't.

Also Swifty, good mobo, i was going to buy that one, but they were out of stock. The asus P5N-D is the same 750i non-reference design as the evga one, just minus the lifetime warrenty.

Aevm, No, i'm not sure how much power it takes. It says it uses 600mA.

here's the link.

http://www.thermaltakeusa.com/Product.aspx?C=1160&ID=16...

I'm certain that my system at full stock with x2 260's would be fine at 750 watts, however, it's all the OCing of both cards and the cpu/ram i'm worries about. I couldn't tell you how much extra wattage i'm using as a result.

I just wanna be sure it's enough before i buy the other videocard.
a b ) Power supply
January 9, 2009 5:56:05 PM

aevm said:
How is that TX850, is it quiet? I might want one too soon.



Actually it is quiet. And it seems to run cool so far. Runs about 14-16 hrs a day on av. The thing about not being modular kind of blows but I can hide the extras away pretty good. it was this or the 1000 watt job...... didn't need it.... saved more than $100. I paid $112 for it.......... pretty good huh?

WICKEDSNOW: there are no problems with that power supply. a friend of mine runs a custom build shop and uses a ton of those........ at least until he started buying bigger stuff....lol........ no problems with any of them. Don't sweat it.
January 9, 2009 5:56:07 PM

Aevm, where did you hear that the 750 i have is really a 825 IIRC?

That would be cool.
January 9, 2009 5:57:25 PM

$112 is a damn good deal on any 850. I paid$89 for my 750. but PC&P are costly.
a b ) Power supply
January 9, 2009 6:04:56 PM

wickedsnow said:
Aevm, where did you hear that the 750 i have is really a 825 IIRC?

That would be cool.



I have one myself :)  I remember reading through the papers I got with it.

Here's a quote from Newegg:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341011&Tpk=S75CF

Quote:

ATI CrossFire Certified (HD 2900XT)
750W Continuous @ 40°C (825W Peak)
High Efficiency (83%); .99 Active PFC
Rock-Solid, Super-Clean DC Output
Automatic Fan Speed Control Circuit


Mind you, the 825W is a peak value, so you can't rely on it too much. Still, other PSUs labeled 750W will shut down or even die if they need to deliver 825W.

I'm guessing the liquid CPU cooler consumes 600mA*12V so it's totally negligible. No worries about it then.

January 9, 2009 6:52:34 PM

Swifty, thanks for the link to the PSU calculator!

It says my current system (inc OC) uses 445W of power.

If I add another video card is uses 591W

Now, because my card is OCed bigtime, I used the OCed ED of the GTX 280 on the PSU calculator, just to be sure. And it still says only 591W used. (ALL overlocking INC, and my thermaltake bigwater.)

Should I use any margin of error? 750-591=159 left. (and i used OCed 280's for the test)(not the 260's i own)

Sounds to me like i'll be ok, unless i'm missing something, like voltage drops, or PSu effiency, or margin of error.
a b ) Power supply
January 9, 2009 7:31:06 PM

Your PSU can deliver 60A*12V = 720W on the 12V circuit.

If you make it deliver 591W it should work all right. It is out of the optimal range, because 591/720=82%, but it will be OK because that's a good PSU and its efficiency doesn't drop that much when pushed beyond 70% or whatever.
http://www.anandtech.com/casecoolingpsus/showdoc.aspx?i=3040&p=11

You will get about 80% efficiency, instead of the ideal 85% or 86% possible with that PSU and a lower load. That's still decent IMO. The noise should start going up, but not really that bad, according to this chart:
http://www.anandtech.com/casecoolingpsus/showdoc.aspx?i=3040&p=15


January 9, 2009 7:39:11 PM

Both you guys have been a great help to me, so thank you both. I'm going to go ahead and buy the other GTX260 core 216 like i want and OC it also. A few posts up, i mentioned that for (just in case) I used the OCed GTX280's for the PSU calculator and not the 260s. If i use the SLI 260s it tells me my wattage used is 498W.

Thanks guys!
a b ) Power supply
January 9, 2009 7:58:49 PM

LOL, I missed that. Yeah, you'll be fine.

Make sure you get some serious cooling. The GTX 260 SLI is one of the hottest things in PC history.
January 9, 2009 8:04:14 PM

Ouch seriously? My current one fully OCed is running a static 70% fan speed and 55C while playing games. but i suppose it's because there not another card right next to it? My 750I Asus mobo doesnt give me more than 1/4 inch between both card.s (when i buy the other one).

My case has x2 250MM fans on the door side of the case blowing on the cards.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

My case :) 
a b ) Power supply
January 9, 2009 8:17:53 PM

aevm said:
LOL, I missed that. Yeah, you'll be fine.

Make sure you get some serious cooling. The GTX 260 SLI is one of the hottest things in PC history.



I have 2 OC'ed GTX260's. Before my sli set up I had both cards running alone in separate machines. One was in a core2 dua with a Corsair 520. the other was in an old AMD machine with a 650 watt Cooler Max ... i think that was the name...?? the one with the 650 ran hotter than the one in the 520. when I swapped them out and made an sli set up with the 850 Corsair both cards ran cooler. I'm not saying they don't get hot......... the warmer weather proved that, but different set ups ( boxes/sufficient power/ cooling ) all make a difference.
January 9, 2009 8:32:01 PM

Thats a few interesting point Swifty. I'll buy the card and check it out. If both OCed make too much heat, i'll just put the fans at 100% all the time on. And deal with the noise.
!