PSU Ratings and Video Card Minimums

I'm thinking of adding a second 9800GT but I'm having trouble deciphering the minimum PSU watt requirements and the video card's specs. I can do the W=I*E etc. math but I can't reconcile the total amps needed as I figure it for two cards and TigerDirect's recommendations for SLI. Only a 2 amp increase???:confused Or is that for each card?Can someone explain what I should be looking for? Thanks.

 

First I'd want a PSU with multiple 12v rails....NOT just one!

Next, why not just go for a 650 and make sure you have enough power for your system, even if you later decide to add more RAM, a second DVD burner, add-on PCI cards, a bunch of USB devices, etc.

I recently upgraded my own PSU from a very good 485w unit to an "Antec Earthwatts 650", with not one, but THREE +12v rails.
It also comes with every imaginable power connector that you'd ever need for a PC. This baby weighs in at a hefty six pounds.
It's not a lightweight by any stretch of the imagination.

I just picked up another one on Thursday in Orlando, for $49..... a real steal!
It will probably wind up in my #2 system.

But, be aware that the wattage printed on the outside of a PSU, or in the sales ad's, is the "Maximum Peak Wattage", required for about one second, to power up a PC, start all the fans and drives and charge the motherboard capacitors.
De-rate that by as much as 25 to 30% for the All-Day operating wattage.

Many people will buy a 350 watt supply when they should be buying a 500w supply.

There's no such thing as a PSU that's too big, but having one too small that shoots craps on you, will ruin your day.:cry

Happy Holidays!
The Shadow :cool

 

Thanks for the response The shadow, I understand peak watts and I stay clear from those specs. My issue is if one 9800GT takes 26A as stated then shouldn't two cards take 52A +4A for SLI which equals 672 watts instead of the 450 they suggest? Could this be just the way they wrote it, each card needs 450W in SLI? As they specify this as 'minimums' I would think that at least 500W PSU would be needed for each. I am totally confused or is my math wrong?

Anyways, I have an Earthwatts 500 and it's not even warm OCing the CPU and GPU 630/1800/950 folding 24/7. Great PSU!

 

I'm anything but a Video Card Expert, but I'd just think that 26A would be one heck of a lot of power for just a video card.
Doesn't a video card take more than one voltage? Like +5v and +12v ??

I used to design and build regulated power supplies, but as I said, I'm a real novice when it comes to video cards and how much power they require.

You've got a good'n there with that Earthwatts 500.
I sure do love my 650.

Good Luck, and Happy Holidays!

The Shadow :cool

 

Thanks Shadow, Happy Holidays to yourself and your family. I'm receiving the second card next week, so let's see what this 500W puppy has to offer!:-D