650w enough for 3 GTX260s or GTX275s?

[newtekie1]

This will be a dedicated 650w power supply for just the graphics cards, the rest of the system will be running off a second power supply.

The power supply has two 12v rails, 30A each, with a 650w max combined on the two 12v rails.

[jjFarking]

Two GTX 260 video cards operating in SLI mode use a combined total of 380 watts and 32 amps at full load. So, 3 would be a tad higher, but the 650w you're referring to should be just fine, even if using the 275s

[BUCK NASTY]

Are you loading them 24/7 like in F@H?

EDIT: just for the GPU's? Should not be a problem.

[theonedub]

Should be no problem for the 260s. Is that a dedicated GPU PSU or a normal 650W PSU you will be using solely for the GFX?

I think that with 3 275s you will be pushing it, as (IIRC) a fully loaded 275 pulls ~220w. Three of those would have a total amperage of just over 54A which is just at the limit of that PSU.

EDIT Maybe I have over looked or failed to include the power drawn from the board in my figures Should be fine

[DirectorC]

I wouldn't run tri-SLI on anything less than 750:

[newtekie1]

Originally Posted by BUCK NASTY

Are you loading them 24/7 like in F@H?

EDIT: just for the GPU's? Should not be a problem.

Yep, F@H 24/7 will be the main use. I looked at W1z's power charts and it seems a GTX285 pulls ~220w maxed out, since some of the power will be provided by the board off the second power supply I should be fine right?

[BUCK NASTY]

Originally Posted by newtekie1

Yep, F@H 24/7 will be the main use.

Very nice. Do you have a kill-a-watt meter? If you already have the PSU and want to avoid buying new hardware, load up the GPU's with F@H and check the power draw. Stay under 80% of the PSU rated power for 24/7 operation.

[newtekie1]

I do have a kill-a-watt, I could also use my 1000w UPS to measure the power draw, I've got the power supply, but not the cards. I kind of wanted to get some opinions on if the PSU can handle it before buying the cards. Of course, if it can't I can just run one of the cards off the other power supply.

[DirectorC]

I'm sorry I didn't clearly read everything you said when I replied LOL. And that LOL is on me. At least you get a nice little graphic of what the full power draw is of a 3-way SLI system with these types of cards.

[bogmali]

Mike047 did just that with his Rosewill 650W PSU powering 3 GTX260's back when he was insanely folding

[TIGR]

That PSU will be easily enough for the 260s (I'm assuming it's not some generic junk). I'm not familiar enough with the 275s to comment there.

[francis511]

My OCZ 600w would shit itself with a gtx 275 , hence the the need for my current psu. In my experience , you always need a bit more than you think you`re going to need (or I build very demanding rigs !!)

[newtekie1]

Originally Posted by TIGR

That PSU will be easily enough for the 260s (I'm assuming it's not some generic junk). I'm not familiar enough with the 275s to comment there.

I've decided on this power suppply: http://www.newegg.com/Product/Produc...82E16817153039

Max 12v combined is 56A, so really 672w.

I've also got this power supply laying around: http://www.newegg.com/Product/Produc...82E16817153070

But the 80mm fan is sort of loud...

Originally Posted by francis511

My OCZ 600w would shit itself with a gtx 275 , hence the the need for my current psu. In my experience , you always need a bit more than you think you`re going to need (or I build very demanding rigs !!)

I doubt that, my main rig with a GTX285 and a 9600GT hardly breaks 450w under load...

[zithe]

Originally Posted by newtekie1

I've decided on this power suppply: http://www.newegg.com/Product/Produc...82E16817153039

Max 12v combined is 56A, so really 672w.

I've also got this power supply laying around: http://www.newegg.com/Product/Produc...82E16817153070

But the 80mm fan is sort of loud...



I doubt that, my main rig with a GTX285 and a 9600GT hardly breaks 450w under load...

OCZ are junky lately. You probably have a much better PSU.

[TIGR]

I might be losing it a bit here ... in that link I'm seeing a Thermaltake with 72 amps on the 12v, not an OCZ with 56. (http://www.newegg.com/Product/Produc...82E16817153039)

[newtekie1]

I thikn Zithe was talking about francis511's OCZ.

Though the quality of the PSU wouldn't really affect the amount of power used by the computer, even a crappy OCZ should be able to handle my main rig considering it only pulls 450w from the wall under load.

[theonedub]

Originally Posted by TIGR

I might be losing it a bit here ... in that link I'm seeing a Thermaltake with 72 amps on the 12v, not an OCZ with 56. (http://www.newegg.com/Product/Produc...82E16817153039)

I apologize in advance if you already knew this, but I think its important to know-

With multiple 12v rails (in 99.9% of PSUs) you do not add the amperage (18+18+18+18) to get total output. Usually there is a max wattage available for all 12v rails, divide that by 12 and there is your max amperage. The Thermaltake label is not very clear, but NT1 prob got the information from the manu website.

Take for example my Antec TruePower New TP-750 (newegg: http://www.newegg.com/Product/Produc...82E16817371022) has 4 25a 12v rails, its max combined Amperage on the 12v is not 100, its 62.

[newtekie1]

The newegg page and Thermaltake's page both list 56A as the max for the 12v lines on the PSU I posted, it just doesn't say it on the label.

The VGA power supply I have maxes out at 54A across both rails, despite it listing 30A per rail.

[nt300]

Originally Posted by newtekie1

This will be a dedicated 650w power supply for just the graphics cards, the rest of the system will be running off a second power supply.

The power supply has two 12v rails, 30A each, with a 650w max combined on the two 12v rails.

I don't think so, you probably have other hardware in your system. To be safe I would go for a good 750W minimum. Do not go bellow 750W or you will have issues with stability and crashes IMO.

[newtekie1]

Originally Posted by nt300

I don't think so, you probably have other hardware in your system. To be safe I would go for a good 750W minimum. Do not go bellow 750W or you will have issues with stability and crashes IMO.

Failure to read what you quoted? The rest of the system will be run off a different power supply.

[nt300]

750W is still the safer bet when running SLI or Crossfire in 2 to 3 way IMO. But thanks for pointing that out to me.

[TIGR]

Originally Posted by theonedub

I apologize in advance if you already knew this, but I think its important to know-

With multiple 12v rails (in 99.9% of PSUs) you do not add the amperage (18+18+18+18) to get total output. Usually there is a max wattage available for all 12v rails, divide that by 12 and there is your max amperage. The Thermaltake label is not very clear, but NT1 prob got the information from the manu website.

Ahh, thanks—I did know that but when I didn't see a max listed on the PSU label, I figured there was no overall 12v cap. I thought they had to be on there so your post is much appreciated.

By the way newtekie, if you want to avoid some finagling with 12v rails, I couldn't recommend the Corsair 750TX more highly. 4x 6+2pin PCIe connectors to boot. You've probably already considered it, but just to throw it out there. The good thing about multiple 12s is that usually there's some leeway and if they say the max per rail is 18a, you can usually still squeeze 20+ out of them safely (within the overall 12v cap) since they're almost never truly independent 12v rails, more often all split from one rail.