Needing a power supply

InnocentBystander · Post by **InnocentBystander** » 2005-11-12 08:46pm

I've got a new XFX 7800gt graphics card, but I'm worried about using it with my machine's stock power supply. The manual says I need a 350+ watt PSU that does 12v with a 20amp current. I did some looking and foud that very few power supplies in the price range that I'm comfortable with (<$75) offer this kind of err performance? The antec 500w are close, 12v @ 19a, but I'm not interested in spending $100 for something that isn't powerful enough.

So I ask, do I honestly need a PSU that meets the volt/amp requirement (stock is 400w and something like 17a at 12v). Can anyone suggest a PSU that will fit my needs that's not going to be overly expensive?

I did some searching on newegg and only found one which meets my requirements JustPc?, never heard of the brand, though the 5 reviews at newegg are good.

Can anyone offer up a suggestion to another PSU to use, perhaps something cheaper, I don't think I really need a 500w power supply when a good 350 or 400w for less would be enough.
Of course, I understand the importance of the powersupply, and that it's better to get a good component rather than fry something, but really, I don't want to spend $150 bucks on one of those high end OCZ ones if I don't need to.

Uraniun235 · Post by **Uraniun235** » 2005-11-12 11:41pm

The 7800 doesn't need 20 amps, they just figure anyone who has a power supply that can do 20 amps on the 12 volt should have enough juice for a comfortable safety margin.

HardOCP had this to say about the 7800 GT:

Another great thing about this card is its power requirements. A 350-Watt power supply is recommended and the total draw of the card is around 75-80 Watts, so it is very power friendly relatively speaking.

Figure out how much juice the rest of your system needs with the SH/SC Power Supply Guide, and from there you should be able to figure out how much power you really need.

InnocentBystander · Post by **InnocentBystander** » 2005-11-12 11:59pm

Does the fact that the XFX is somewhat overclocked increase it's power demand any?

Pezzoni · Post by **Pezzoni** » 2005-11-13 11:22am

Have a look at Hiper power supplies, whilst they're relatively new to the market, they have a good reputation. Not too pricy, either.

Uraniun235 · Post by **Uraniun235** » 2005-11-13 02:15pm

InnocentBystander wrote:Does the fact that the XFX is somewhat overclocked increase it's power demand any?

Perhaps, but I doubt it would be that much bigger.

InnocentBystander · Post by **InnocentBystander** » 2005-11-13 02:20pm

Some research showed that the XFX's draw is 100watts. How many amps on the 12v would that come out to, about?

phongn · Post by **phongn** » 2005-11-13 03:53pm

InnocentBystander wrote:Some research showed that the XFX's draw is 100watts. How many amps on the 12v would that come out to, about?

P=IV, so you'll need around 8.33 amps just for your GPU.

InnocentBystander · Post by **InnocentBystander** » 2005-11-13 03:57pm

Then it sounds like I really will need a 20amp PSU, to be on the safe side.

InnocentBystander · Post by **InnocentBystander** » 2005-11-13 04:12pm

another side question, by using the 2 4pin flat power connectors to 1 rectangular 6pin PCI-E power connector are my amp requirements going to be any less (splitting it up might require less current? I don't know...)