Need help with psu

dacviet

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Jan 24, 2010
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hello, i just bought a geforce 9800 gt and noticed i wasnt getting the fps i should be (10-20fps) around alot of people. so i was told that i should upgrade my psu, i purchased a thermaltake 550w psu and installed it. still getting the same fps, and im wondering that the gfx card minimum power requirements is 400watts and 12v @ 26amps. the psu i bought has dual 12v @ 17amps. shouldnt that somewhat be an improvement? im new to all of this and dont really understand much about the power supply stuff and any info would be greatly appreciated :)
 
That was a waste. Your power supply has nothing to do with the performance of your computer with the exception that if it does not provide enough power at any given time and system load, your computer will randomly shut down.

two 12V rails at 17A each is the same as one 12V rail at 34A. The +12V rail provides power to the CPU and graphics card among other things that use virtually no power. The power provided to these components is found by P=EI or power =voltage x amperage. so in the case of your older power supply, 12V*26A=312W. But power supplies are inefficient. 80% efficiency is common so 312W*80%=250W. So you would have about 250W to run a 9800GT and whatever CPU you have. However, like I said, your computer will randomly shut down or reboot if not enough power is being supplied.

Now that you know your power supply does not affect performance, we'd be willing to help you determine your problem if you share your system spec, especially your CPU aswell as the games you are playing, the resolution and settings you play them at.
 

dacviet

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Jan 24, 2010
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18,530
oh i see, so i guess i'll return the psu tomorrow then and get something else that might help my computer? im running HP Pavilion it has a AMD phenom x3 2.1ghz, and 3gb ram, the game im trying to play is wow. im just trying to get my fps up in 25man raids cause raiding with 10-20fps really sucks and its not even that fun :(
 

4745454b

Titan
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OP, looking at what you've told us so far I'd be inclined to think the problem is with your first gen Phenom. It has three cores, and a low IPC and frequency. This CPU will struggle with something like Raiding. Your problem is going to be in upgrading it. HP might not have wrote a bios for the mobo to support anything faster/better. You can try using CPUz to see what chipset it has and HPs website to see what CPUs it supports.

Not quite Enzo. There are several things wrong with your post.

12V rails at 17A each is the same as one 12V rail at 34A.

While its possible for this to be the case, it isn't always like this. The Antec Earthwatts 500W PSU is a good example of this. When Seasonic made the PSU it had two 12V rails, each rated at 17A, total output power of 34A. Antec switched to Delta later to make it, and the specs changed slightly. Delta raised the OCP to 22A per rail, but the 12V rails combined stayed at 34A. Using your math you would have thought the total was 44A, but its not. To figure out how much power you have the 12V rails, you have to find the information on the PSU and use the correctly provided formula. As a general rule, I suggest avoiding any PSU that fails to list either total wattage or amperage.

But power supplies are inefficient. 80% efficiency is common so 312W*80%=250W.

Doesn't work that way. Efficiency is how well a PSU can convert AC electricity to DC. The more efficient a PSU is, the less electricity you'll pull from the wall. Look at any PSU review and you'll see this is the case.
 

Right. A PSU that was 80% efficient would need to pull 390 watts from the wall to provide 312 watts to the computer.