450 enough for sli?

[dywolf]

gonna replace my older 7960gt with a pair of EVGA 8800GT SSC (N806's), and honestly not quite sure if my PSU has the oomph to handle it. theoretically, and according to the calculator, it does, but I wonder what personal experience from people says. I know it can handle a single but I never done an double card setup so I ask:

X2 4600+ (GA-M59SLI-S5 Gigabyte board with 2gb ram)
2 8800 GT in SLI
2 80 SATA drives (mirror raid)
4 80mm fans (2 rear, 1 front, 1 side)
PCP&C 450w Turbo cool, 2yrs old

run a pretty simple system, i dont need much for what I do, especially being on the "broke college student" budget. been looking at maybe replacing the case (NZXT Guardian) in favor of one of those sweet looking antec 900's, but that's more of an aesthetics and noise motivation than real neccessity. anyhow, enough ramblin

 

[Quiksilver]

Probably not, I would at least want 550W minimum.

 

[MarcVenice]

Some poeple will say sure you can. I'll say, why not just try, if it boots, and you're in for an adventure, see how long the PSU will last before it starts squealing and then goes out with a puff of magic smoke. It shouldn't take out any of your components, but you will end up with a dead powersupply. Personaly, if you can afford 2 8800gt's, you can spend 100$ on a PSU, a decent 550-600w psu that is.

 

[jonmcc33]

According to AnandTech you can...

http://www.anandtech.com/video/showdoc.aspx?i=3140&p=13

FYI, no need to list fans. They don't really use any power worth considering.

 

[mpilchfamily]

Do NOT try a PSU that might be too small. If it is too samll and the PSU pops there could be other damage done to the system. Now most 400W PSUs don't offer sufficient amperage on there +12v rail to support SLIed 8800GTS. You want a PSu that can offer more then 32A on the +12v rail.

The Antec 900 is an excelent case and only gets noisy if you have all the fans turned up to full speed.

 

[imported_Scoop]

If the PSU has two PCIe cables, then it should work, I'm kind of thinking it doesn't though.

 

[mpilchfamily]

Not all SLI certified or non certified PSUs with 2 PCI-e power connectors can run all SLI setups where each card only uses a single connector. Many 450W to 500W PSU that have 2 PCI-e connectors are not able to run a pair of 7900GSs. There are even some PSUs that are nearly 600W and have SLI certification that can't run it either.

 

[Yellowbeard]

IIRC, 8800GT = 150w-170w under load. So, let's say SLI = 300w for the cards, 300w/12v = 25a. And, that is not including all of the other goodies pulling on the 12v rail. So, check the 12v rail spex on that unit. PC P&C is good quality so it "might" do it "IF" the 12v rail is strong. As Mpilchfamily noted, 32a or more is a good idea.

 

[imported_Scoop]

Originally posted by: Yellowbeard
IIRC, 8800GT = 150w-170w under load. So, let's say SLI = 300w for the cards, 300w/12v = 25a. And, that is not including all of the other goodies pulling on the 12v rail. So, check the 12v rail spex on that unit. PC P&C is good quality so it "might" do it "IF" the 12v rail is strong. As Mpilchfamily noted, 32a or more is a good idea.

8800GT pulls 75W from the slot and another 75W off the pcie cord so if my math isn't way off, 150W is theoretical max. If the increase using a system with a single 8800GT to SLI was FROM THE WALL around 118W as stated HERE, the card actually has a DC draw of under 100W, which actually sounds a lot more reasonable than your calculations.

 

[MarcVenice]

Ya, around 100-125w is more realistic. 150-170w are 8800gtx like numbers.