8800GT Power Requirement Confusion

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SoSilencer

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Like everyone else I'm building a new comp with an 8800GT and need PSU advice. I thought I had it figured out but after reading the forums a bit I've gone and confused myself. I actually have a specific question though... nVidia seems to recommend 400w with 22a 12v for a single 8800GT or 450w with 24a 12v for SLI. Does this get split between the PCIE slot and the extra power connector or does all the power have to be on the same rail? How much power per rail is really needed to run an 8800GT?

Since I have the original FSP Blue Storm AX-500A I was looking at the FSP Blue Storm II (http://www.newegg.com/Product/Product.aspx?Item=N82E16817104034) but it has two 18a rails which seem like they don't meet the above requirements. The Corsair 450VX (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139003) seems to be really popular here and has a single 33a rail so that seems like it would be a safer choice but maybe there are better options? Specs for the machine will be Q6600, 4gb ram, 8800GT (probably overclocked EVGA 700/2000mhz), 2+ HD and 2x dvd.

Also I noticed that some motherboards have an 8 pin cpu power connector and this is not something I'm familiar with. The Corsair 450VX seems to have a cable for this but many PSU don't. If that Corsair unit isn't adequate for this machine, what spec/rating/title should I search for with a PSU to know that it has all the right cables?
 
Those power supply specs are for the entire system, not just the video card. If you did not have that quad core I would say you would be fine as you have about 30A of +12 available (I did not look up you power supply but typcially due to the Total Power Output ratings you would not get all of the 18A + 18A = 36A of 12V power.

we can worst case it, the new PCI-E 2.0 spec allows 300Watt per device installed in a slot. Thats 300/12 = 25A.

However up to 75W is supplied by the power going to the slot itself, leaving 225W max through the PCI-e power connector from the power supply. The slot power comes from the motherboard power connector and/or the aux 12V so 225/12 = 18.75A absolute max current draw for a PCI-e connector going to a single video card. (This assumes the video card bothers to conform to the spec)

I seem to remember one of the 8800GT reviews saying the card draws about 130W which is about 10A.

anyway you are not as bad off as you think.
 
Well, it's better to post here than start a new thread. I already have my 8800GT, but I fear my PSU may not provide enough power on the 12V rail. (For specs, see the Newegg page.)
 
The 8800GT uses 110 watts. That equates to a 9.2amp draw from the 12v rail.
 
deddyeka said:
for power supply better use the big one.
the safer the better.
Click to expand...

Power consumption for this thing is weird. It seems to use more power than the GTS, but it's maximum power consumption is still less than the GTS (it "tops out" at a lower power consumption figure.)

Use at least a 500W for a single card and a 600W for SLI. Try to avoid two +12V rails for SLI unless the PSU has more than 20A on each +12V rail. Single +12V or four +12V rails should be more than adequate.
 
I recently had to replace the stock PSU in my Dimension 4700 with a Thermaltake 430. I'd like to move from my 6600GT to the 8800GT but I figure it would probably melt my poor power supply.
 
Ugh... TT 430W? Waht were you thinking? ;)
 
I was having trouble finding something that would fit the Dell's slightly funny case design. In the end the Thermaltake was the only one other than Rosewill that looked like a match that was less than $100+ and had plenty of favorable reviews over at newegg.

It does fine in that machine, quieter and cooler than the factory PSU but like I said it would not be good for something like the 8800GT.

I don't have much experience with PSU selection so I got as much info as I could and went for it. :D

EDIT: I know you've given good reviews to TT PSUs in the past, what makes the one I bought such a dud in your eyes?
 
jonnyGURU said:
Power consumption for this thing is weird. It seems to use more power than the GTS, but it's maximum power consumption is still less than the GTS (it "tops out" at a lower power consumption figure.)

Use at least a 500W for a single card and a 600W for SLI. Try to avoid two +12V rails for SLI unless the PSU has more than 20A on each +12V rail. Single +12V or four +12V rails should be more than adequate.
Click to expand...

45Nm
 
Cirkustanz said:
45Nm
Click to expand...

65nm.

And that would be an explaination for power consumption that was less across the board when compared to a 90nm die, but it's higher on average I have found. My best guess is because additional GPU bottle necks are being freed up with the additional stream processors, faster core clock and faster shader clock, but then tapers off because there's really only so much the card can do. Just a guess.
 
jonnyGURU said:
65nm.

And that would be an explaination for power consumption that was less across the board when compared to a 90nm die, but it's higher on average I have found. My best guess is because additional GPU bottle necks are being freed up with the additional stream processors, faster core clock and faster shader clock, but then tapers off because there's really only so much the card can do. Just a guess.
Click to expand...
It also has a lot more transistors, and all of the silicon for the video decoding engine now doesn't it?
 
I'm headed for the same quandry. I'm migrating my 8800 GTS into the system with the 8600 GTS, and so far my OC'd Core 2 @ 3.2 is fine. I have 3 HD, 1 DVD and X-meridian, and wish to switch to P6N-SLI + 2x 8800GT since my GTS just isn't enough for me at 1920x1200. Think my dual 12V HEC 12V1=+19A 12V2=+20A will cut it? I already have the P6N, and I'll be moving everything else into that case. Picked up the Cooler Master 690 on the cheap, and wow is it a nice case - build quality screams attention to detail.
 
I think you'd be cutting it VERY close if it does work. I personally wouldn't risk it, not on an SLI setup.
 
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