What PSU to choose for my needs?

[sata]

Hello all

I am new here and hope to provide help to others

I am confused about power requirements for the 8800GTX and hope you will shed some light on what PSU to choose.

Other sources have different opinions for my questions


I am going to be building a new system and it goes something like this:
E6600 / E6650
2 GHZ DDR2 800MHz
A 680i based MB
3 SATA HDDs
8800GTX

I might upgrade in the future to a GPU dedicated to physics when this solution will be available, and I guess it will be either a 8800GTS/GTX, or an older 7900 if it will be possible/powerfull enough for physics. So in the end I will have 2 GPUs when the physics solution will be available

I want to know the wattage and amp requirements for the 8800GTS and for the 8800GTX, has anyone checked this in some review?

I have searched for many PSUs and have come to a conclusion the best choise is the Corsair HX 620W triple 12v rail

It will surely be enough for the 8800GTX (asuming the GTX does not take more than 18A)

So one rail will be for the graphic card, another for the CPU and another for the 3 HDDs, DVD rom etc, but is there more room for another graphic card?

Then im good with one card, but will I be able to add another 8800GTX or GTS for the physics work in the future (or to run in SLi for that matter)?
Will it have enough wattage, and more important, will it have enough amps and where will it take them from?

That is what I wonder about... I sure hope this PSU will be enuogh for 2 graphic cards. My other option is a quad rail PSU, but it is not modular or as good as the Corsair (It's an Epsilon 600/700W).

Thanks for the help :)

[burebista]

For an OC-ed Kentsfield and one 8800GTX was enough an Antec Phantom 500.
For an OC-ed Kentsfield (Vapochill LS) and 2x8800GTX (ice cooled) an Tagan U25 700W was enough (http://www.crazypc.ro/forum/attachment.php?attachmentid=17412&d=1164541655) (max 0.08V drop on 12V). Some pictures (http://www.crazypc.ro/forum/showpost.php?p=81423&postcount=4) with that setup.
So, I'd say that you'll be safe with Corsair 620W.

[sata]

Safe with the Corsair 620W for 2 8800GTX cards?

I would like to know how much amps/amperage each takes and if this PSU has enough

It may run 2 GTX but maby they wont give full performance because of not enough Amps

[jonnyGURU]

First off, the Corsair doesn't really have three rails. Which is good in your circumstance.

The 620W would probably be enough, with the only hang up being the fact that the unit only comes with two PCI-e connectors.

But it's hard for anyone to say for sure. Right now, the cards aren't using much more power than an ATX X1950XTX, but once DX10 comes out and the cards can really come out of their shell, they can use as much as 18.75A each.

So it's good to plan on the high side, or wait until bigger PSU's come out that meet your criteria (quiet, efficient, etc.)

[sata]

What do you mean that it does'nt really have 3 rails? So how does it work? And why is it good for me

2 PCI E connectors is what the PSU can support, there is'nt any more room to connect more than 2, and now I wonder how will it be able to work for SLi, and 2 8800 will need 4 PCI E conectors?

Is'nt it one rail to the CPU, one to the hhds etc and one for the graphic card? And if its so, then how will it be enough for 2 8800GTX

Also I wonder if this is really true, from Corsair site: "Triple 12V Rails provide independent reliable power to the CPU, video card and other components with a combined rating of 50A (40A on 520W) maximum! Advanced circuitry design that automatically enables power sharing between the triple +12V rails in an event of overload on any single +12V rail"

Also is there some site which checked the wattage and amp usage for a 8800GTX/GTS on DX9 titles?

[jonnyGURU]

What do you mean that it does'nt really have 3 rails? So how does it work? And why is it good for me

How does it work? It's just one 12V rail! :) There isn't three in the first place. That's just what the label says. ;)

2 PCI E connectors is what the PSU can support, there is'nt any more room to connect more than 2, and now I wonder how will it be able to work for SLi, and 2 8800 will need 4 PCI E conectors?

Well... nice thing about modular PSU's is it gives the PSU manufacturer an opportunity to provide "upgrade cable kits." I'm willing to bet Corsair will offer a 1-into-2 PCI-e cable for their HX PSU that will allow it to work with a pair of 8800GTX cards.

The alternative is to use the 2-Molex-to-1-PCI-e adapter that comes with the card.

Is'nt it one rail to the CPU, one to the hhds etc and one for the graphic card? And if its so, then how will it be enough for 2 8800GTX[quote=sata;4818]

No. It's not. That's just what the label says. It's one 12V rail. :)

Typically, yes... it would be one 12V rail for CPU, and then the other two for peripherals and PCI-e, but that's not actually the case w/ the recent Seasonic built offerings.

[quote=sata;4818]Also I wonder if this is really true, from Corsair site: "Triple 12V Rails provide independent reliable power to the CPU, video card and other components with a combined rating of 50A (40A on 520W) maximum! Advanced circuitry design that automatically enables power sharing between the triple +12V rails in an event of overload on any single +12V rail"

I LOVE this fluff. It's fantastic. But think about it....

If a rail is ALLOWED to be overloaded, and therefore can provide more power to peripherals... why bother with an over current limiter at all!?!

Also is there some site which checked the wattage and amp usage for a 8800GTX/GTS on DX9 titles?

The most any PCI-e card can use right now is 225W. That's per PCI-e spec and confirmed with nVidia. Currently, power draw reports with the G80 haven't been that great, but without DX10 drivers and utilizing the card's full capability, it's not going to be. :) And then you have other bottlenecks like CPU, RAM, motherboard, etc. But AT THE MOST, you're looking at 225W per card.

[sata]

Thanks for your answers

Will it be possible to use 2 pcie connectors for one gtx, and two 2-Molex-to-1-PCIe cables for the other card (for sli)?

If the gtx takes as much as 225W, that's 450W for 2, and you are left with 170W for the rest of the system, which probebly isn't enough. I guess we need to wait until January to find out the Wattage and Amp the GTX consumes to see if this PSU will be able to handle it.

thanks

[jonnyGURU]

I would use one PCI-e and one adapter per card.