Psu help

Hi, looking to purchase a 7900gs video card, requires 20amp on the 12v rail and a 400 watt power supply , do you add up the dual rails for this im alittle confused on this . I have been looking on newegg for a power supply but i would like it to be under 60 and it has to have a 6 pin connector but the card comes with a 6 pin adapter Rosewill RP550-2 ATX 2.01 550W Power Supply 115/230 V CSA, CB, TUV, FCC, UL would this work any suggestions thankyou

My understanding is that you add the two rails to get the total output of the PSU.

I have been very pleased with Antec and very disgusted with Rosewill so I have a preference towards anything else. If I was looking for something cheaper I would go with Thermaltake or Coolermaster as both are top companies.

Others will have different ideas.

check out FSP Group, they make very good PSUs at reasonable prices…not to mention they are the OEM for several high end PSU brands

Yeah, I’ve got a FSP 350W PSU, it’s really nice and quiet too. :slight_smile:

Thinking of getting another (maybe a bit beefier) as backup.

Here’s is one that should fit your needsAntec Smartpower 450W. Have you figured up how many watts your system will actually need? It’s important that you know b/c too little power can cause many problems (random shutdowns, component destruction, etc). Usually I would recommend at least 10% more than the sum of your components max usage. Also, don’t skimp on a PSU since it is the often overlooked heart of your system.

here is an FSP 450W with a tad more on the 12v rails than the antec (of course it has to be out of stock right now at newegg :rolleyes: )

and as jhtalisman said, don’t skimp on the PSU…if you plan to get SLI and/or overclock and/or get a bunch of HDDs/ODDs you will need to get something 550+ watt with 36-40+ amps (combined) on the 12v rails

here is a PSU calculator that will give you some idea how much power you will need

Most PSU calculators will automatically add at least ten percent to the total, and I would go larger than what they suggest. A larger PSU won’t hurt, and you can always add more toys.

With a PSU that has dual 12V rails you want the amperage of either rail to be able to support the current draw of the GPU, the combined amperage dosen’t matter as the card will only draw from one of those rails.

If you want quality, (makes PSUs for Corsair among others).


I got this baby and it powers… quite a lot of things to be honest and doesnt even speed up(!) making it very quiet.
Athlon 3200+, 2 * Hitachi T7K250 250Gb, 1 * Hitachi T7K500 320Gb, BenQ DW1650, 2 * 512Mb RAM, DVB-T card, Saphhire Radeon 1950XT (I belive ATI/Sapphire recommends a 450W PSU for this one heh). SilentPCReview has a review of it and Xbitlabs got one of its bigger brother 500W, both showing very good results.

If you want budget PSU (it gets pretty nasty when its loaded though)…

At least one with a 120mm fan…
//Danne

thanks for the help, one more question can anybody recommend a good motherboard for performance and a non sli board dont want to break the budget , i was looking at the a8n-e, i built one with a a8n5x im very please with it , like to stick with amd, thanks.

What are you going to be using this for? What kind of budget do you have? What CPU are you going to use?

amd64 3700 939 socket, gaming mostly, but im not going sli just one card , under 100 for motherboard

I just did a build with a Biostar TForce 6100 939, good onboard graphics and audio, up to 4GB of RAM, dual channel. Check it out here.

If you’re into overclocking check out the BIOS.

thanks for the response , but i would like more pci slots any other suggestions


How about that?
//Danne

thanks for the response, still 7900gs requires 400watt 20 amps on the 12v rail .my question is if i get a psu 400 watt or 450 watt and the dual rail is 18 on 1 and 16 on the other is this enough for this card, some say gpu draws from just one rail , if this is true the power supply wont be enough, please helppppp.

I could be wrong, but I recall that most of the specifications for these cards list a recommended power supply. This does not indicate what the card draws but is a guideline for the total power needed to run your entire system. You should be fine and the 7900GS is a lower power user than other cards in the same class.

“So indeed, you need 350 at the least as you want some spare wattage and 420 Watts or better is definitely recommended. When you buy a new PSU then look at the packaging and check the 12 volts rail on Ampere, it should be 22 AMPS minimal (for the total of +12 volts rails).”

http://www.anandtech.com/video/showdoc.aspx?i=2874&p=20


thankyou, it cleared alot up for me.

The “suggestions” made by the manufacturers is not really a guide line, they suggest that figure for a reason. You will be better served if you purchase a reputable PSU with a 12V rail with the ampacity suggested by the manufacturer. Yes there are people out there that have gotten by with less, and then there are those that have had to make two purchases because they didn’t just get by with their first purchase. Caveat emptor!

Chas, have any links or pics on the dual rail setup. I may need to jerry rig my Dell for a new 500w PS and 7600 card.
Thanks man. How cold is it up there? LOL