[Mr. Killjoy]

Ok, the best way to know the theorical amp of a PSU on each rail is to read the manual, though, is there a way to know it in practice
For example I know that my +12V rail should provide 15A, but maybe in reality, it's lower, or higher... so? Any way to know it without opening the PSU and measuring it?

thx

 

[cooliscool]

On the side of your PSU there should be a diagram labeling all of the rails..

Mine:

edit: misinterpreted your question.. you want to know the real amperage of your PSU's rails.. well, not much you can do but get an ampmeter and open it and measure. A theoretical 15A is a bit low, especially since your GPU is drawing from it.. you should look in to a PSU with at least 18A on the +12V.

 

[Mr. Killjoy]

So my 6800 will run underclocked till I sell my organs for a PSU I guess

How much did you pay for this one?

 

[cooliscool]

$70 USD, 350W with 20A on the +12V rail, at CompUSA. Could have gotten much cheaper online (<$40), but I really needed it quick.. good PSU overall, haven't had an issue with all of my devices (2 optical, 2 HDDs, 9800 Pro, Vcore @ 1.7V, Vdimm @ 2.8V, about 8 fans including CPU & GPU, etc..).

I doubt a PSU with 15A on the +12V rail could really run a 6800 at all.. you'll probably get major artifacting due to lack of power.. the 6800 really calls for a good quality PSU with good amperage, especially on +12v.

 

[Mr. Killjoy]

I've read somewhere that when it's too low on power, the driver automaticly underclocks the card to lower the requirements (of course causing an FPS drop, but not worse than using my GF2MX )