Power requirements for 7900GS

[HGL]

Hi Guys,

I've bought the following PSU

Enermax Liberty 400W ELT400AWT ATX2.2 Modular SLI Compliant PSU

and I'm using it with the following graphics card

EVGA GeForce 7900 GS KO 256MB GDDR3 HDTV/Dual DVI (PCI-Express) - Retail

However I'm concerned whether the Enermax 400watt PSU is up to the task of working with the overclocked 7900GS.

The PSU has two 12v rails rated at 20A each. The 7900GS recommended requirements are 22A on the 12v rail and 440watt overall.

The reason I'm concerned is because the PC fails to pick up more than 1 usb device at startup. I have to plug them in after. The other thing that confusing me is whether having two 12v rails makes a difference, so do I have 40A overall (20x2) ?

I know I should ask eVGA directly but I find it easier to ask here, so any help would be appreciated.

 

[Yaka]

i built one for a friend using his shuttle and 200w shuttle psu, runs fine

 

[throdgrain]

My son has one with a 350w psu, runs fine

 

[Kryten]

The 7900GS I've just purchased has a recommended min PSU spec of 420 watts on. (Gainward). Have an Akasa 460 watt PSU however have 4 HDDs and 2 DVDRW's so might be pushing it a little.

I would seriously look at ramping up the power supply - 400w is little even for a decent make like Enermax.


Have to say you're a little unlucky buying that eVGA card - eBuyer have an XFX for 89.95 inc vat and delivery :|

The two rails do not combine at all - they are separated in such a way that your CPU is provided with a stable current as well as your other peripheral hardware - and specifically so should you encounter instability on your peripheral - it doesnt effect the CPU.

 

[HGL]

The 7900GS I've just purchased has a recommended min PSU spec of 420 watts on. (Gainward). Have an Akasa 460 watt PSU however have 4 HDDs and 2 DVDRW's so might be pushing it a little.

I would seriously look at ramping up the power supply - 400w is little even for a decent make like Enermax.


Have to say you're a little unlucky buying that eVGA card - eBuyer have an XFX for 89.95 inc vat and delivery :|

The two rails do not combine at all - they are separated in such a way that your CPU is provided with a stable current as well as your other peripheral hardware - and specifically so should you encounter instability on your peripheral - it doesnt effect the CPU.

I'm beginning to think it's underpowered on the +3v rail which provides 26A because in the H/W monitor according to the BIOS the reading is just under what it should be.

I was a little unlucky buying the enermax, however I only paid £88 for the 7900GS (OCuk have put the price up) so I don't regret buying the Gfx card.

I find it strange that eVGA rec. 22A on the 12V rail yet the best PSU's have up to 4 rails for 12V yet don't even come near 22A on any 12v rail.

I think I will get a new PSU, so according to eVGA forums I should get a 600W just to make sure. They said this one should be good enough.

OCZ GameXStream 600w Silent SLI Ready ATX2 Power Supply

Anyone got any better suggestions ?

 

[Ormorof]

i have a 500W psu and never had any problems (with that card), that said i had a 400W one and that overloaded with just a radeon 9800 in it

 

[Kryten]

Just a thought - you'll have a separate connector for the PCIE graphics card (8 pin? or is it 6) - those will be rated separately from those 12volt rails, check those. Of course if you are using an adapter from 2 molex plugs to that PCIE plug, that could be the issue.

 

[HGL]

Kryten, I changed the Gfx power connector from a pci express to 2 molexes instead to see if it would make a difference, sadly it didn't and I've ended up ordering the 700 watt OCZ Gamexstream which should come 2moro.

Fingers crossed!