Proper PSU?

[velrahnkoon]

Hi all,

I recently put together a quad core-based rig and my PSU has gone bad. I wanted to get some advice as to whether the PSU I have is big enough to power everything, or if I am borderline and should step up to a larger PSU when I RMA the old one. Here are my specs:

Intel Core i7 920 2.66 GHz
MSI x58 Platinum mobo
2 EVGA GeForce GTX 260 core 216s (superclocked edition)
G.SKILL 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Western Digital Caviar WD1001FALS 1TB 7200 RPM SATA
Seagate 320 GB 7200 RPM SATA
LG 22X DVD±R DVD Burner SATA
ZALMAN CNPS9900LED 120mm 2 Ball CPU Cooler
Creative Sound Blaster X-Fi Titanium Fatal1ty Professional
COOLER MASTER HAF 932 RC-932-KKN1-GP Black Steel ATX Full Tower Computer Case (with 3 230mm fans (one of them is an LED fan), and one 140mm fan)
Thermaltake Toughpower W0178RU 850W PSU

So, is the 850 big enough to run this setup? I never ran the numbers before I built the machine, which I should have, but each video card pulls 36 amps peak. I have each video card set up to pull from one native and one modular PCI-E cable.

According to the user manual for the PSU, the modular cables pull from the #2 12V rail, which supplies 18A, and the native cables pull from the #3 12V rail, which supplies 30A. The 24 pin mainboard cable pulls from the #3 rail, and the 8-pin CPU connector pulls from the #1 and 2 rails. So I have each video card pulling from both the #2 and #3 rail, the mobo from the #3, and the CPU from the #2. The peripherals, floppies, and SATA drives pull from the #4 rail.

It seems like this should be enough power, so I'm leaning towards the explanation being that I just got a bad PSU. However, am I running on the "borderline" of what the PSU can supply? IIRC, you're supposed to operate a PSU between 30 and 70% peak to get the best performance. I don't know what the Mobo and drives and CPU pull, so could I be pulling 90+% and that's why the PSU failed, because I was almost at peak for the entire time I've been using it and therefore overtaxing it?

Thanks for any info! I think that either way I may upgrade to a bigger supply when I RMA this one.


EDIT: Now that I wrote all that up, I notice that the spec plate on the PSU says 744W max output on the 12V rails, which is 62 amps max. If the video cards are each pulling 36, that's a 10 A shortfall on just the video cards, not to mention everything else that pulls from the 12V rails.

So I need to ensure that the 12V rails supply 72 A + how much for the other components that use 12V? Basically, what final amperage number should I be shooting for on the 12V rail? I understand that the GPUs won't pull the full 72A all the time, but I need to have that power available regardless, don't I?

Thanks again!

 

[HOOfan_1]

The GPUs won't pull 72A (36A each)....EVER.

The GTX 260 uses a couple of 6 pin PCI-E connectors, which PCI SIG states should pull no more than 75W (6.25A) each and then they can pull up to 75W from the PCI-E slot itself. Added together the GTX 260s cannot use more than ~18.75A (225W) of 12V each. In practice, they won't even use that much power...maybe 150W each at most.

I believe you likely think they will pull 36A because the vendor you bought them from stated that a PSU with 36A combined on the 12V rails was required to run the cards. However, that number takes into account ALL components in a relatively high end computer, that they would expect to be accompanying the GTX 260.

A fully functioning Thermaltake Toughpower 850W is more than enough for the system which you are running.

 

[Zero82z]

A 55nm GTX260 draws about 105W/9A from the +12V rail for the record. Like HOOfan said, the 850W Toughpower will be plenty.

 

[velrahnkoon]

The GPUs won't pull 72A (36A each)....EVER.

The GTX 260 uses a couple of 6 pin PCI-E connectors, which PCI SIG states should pull no more than 75W (6.25A) each and then they can pull up to 75W from the PCI-E slot itself. Added together the GTX 260s cannot use more than ~18.75A (225W) of 12V each. In practice, they won't even use that much power...maybe 150W each at most.

I believe you likely think they will pull 36A because the vendor you bought them from stated that a PSU with 36A combined on the 12V rails was required to run the cards. However, that number takes into account ALL components in a relatively high end computer, that they would expect to be accompanying the GTX 260.

A fully functioning Thermaltake Toughpower 850W is more than enough for the system which you are running.

Thanks HOO and Zero! The highlighted statement above is almost verbatim from newegg's specification sheet

Glad to know that I wasn't overtaxing the PSU. Sucks that I need to RMA it, but at least it wasn't anything I did.

Are there any good PSU calculators out there, or somewhere that I can look up individual components to put together the type of power consumption they have? It'd be nice to know the next time I build a rig.

Thanks again guys.

Vel

 

[vertigomhs]

Thanks HOO and Zero! The highlighted statement above is almost verbatim from newegg's specification sheet

Glad to know that I wasn't overtaxing the PSU. Sucks that I need to RMA it, but at least it wasn't anything I did.

Are there any good PSU calculators out there, or somewhere that I can look up individual components to put together the type of power consumption they have? It'd be nice to know the next time I build a rig.

Thanks again guys.

Vel

the antec psu calculator is pretty good, but the forums are the best place to get advice on PSUs of course .

 

[Dangman]

Are there any good PSU calculators out there, or somewhere that I can look up individual components to put together the type of power consumption they have? It'd be nice to know the next time I build a rig.

Not exactly a PSU calculator but I personally use it to get a ballpark figure and it's fairly accurate:
http://corsair.com/psufinder/default.aspx

I just insert the parts I intend to use, see what PSUs Corsair recommends, then look at their +12V rating and use that a ballpark figure for how much the system needs. Pretty helpful to know what's the minimum +12V rating needed for a certain system. Then see what other PSUs are out there with similar quality and +12V rating and go from there.

 

[Zero82z]

Are there any good PSU calculators out there, or somewhere that I can look up individual components to put together the type of power consumption they have? It'd be nice to know the next time I build a rig.

To come up with my own estimates, I go by the TDP of the CPU in question. To find out power usage when overclocked I estimate using the formula P = C*V^2*f - basically, you divide the TDP by the stock speed of the CPU once and by the stock voltage twice, then multiply the answer you get by the overclocked speed once and the overclocked voltage twice.

For GPU numbers, I go by the power consumption values in reviews performed by X-bit labs whose test rig allows them to directly measure the power consumption of just the video card. If the card isn't listed, I estimate based on the ones that are there.

For hard drives, I estimate about 20W per drive, and for everything else I usually just add 100W (probably more than the actual draw, but better to aim high than low).

The estimates I get with this method are definitely higher than the actual power consumption of most systems, but they tend to be more accurate than most PSU calculators in my experience.