psu 12v rail question

[lee2008]

Hi, i recently purchased a 750w psu and also a hd4870x2 gpu, i am not getting the performance i expected from the card so i have had the motherboard, gpu, and cpu replaced to try and sort the problem out.

I have noticed in a number of programs that give info of a psu's output that the 12v rail is only producing 11.40v even under load (speedfan, sandra lite), is this correct or is it meant to increase the voltage to the rails when its under load i.e running my gpu which uses 428w.

 

[IH8U]

First question, what brand of PSU do you have?

Secondly, it's not wattage that is the concern, but the Amperage.

 

[Amg]

ochh mines doing the oppesit (overvoltage) than it has 25volt on northbridge spzzems o.o but motherboard seems not affect which I hope it is a wrong reading... who makes your psu and what amps should it fire down that 12volt rail ?

 

[IH8U]

Over is fine (as most components downgrade it themselves). Under is BAD!

here is my PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E16817256036
(yes I need to update my sig)

 

[aevm]

I doubt that your GPU uses 428W. How did you get that number? The PCI-E slot and the PCI-E connectors together can't deliver that much.

 

[lee2008]

got the answer from a website somewhere, IH8U my PSU is a Zalman 750W with the specs below:

750w
+3.3v min 0.8a max 20a
5V min0.5A max30A
combined 160w

+12v1 min 0.5a max30a
+12v2 min 0.5a max30a
+12v3 min 0.5a max30a
+12v4 min 0.5a max30a
combined 720w

-12V min0.0A max0.8A
+5VSB min0.0A max2.5A peak3.5A
combined 22.1w

overall 750w

hope that makes sense

 

[lee2008]

the thing is i have a big performance problem with my hd4870x2 i've installed different versions of windows including xp 32bit and 64bit, vista 32bit 64bit, changed cpu, motherboard, i've even changed gpu because i thought it might be that!

installed all chipset drivers ati driver including 8.8, 8.9, 8.10

any ideas

 

[leo2kp]

Performance in what application exactly?

 

[lee2008]

every game i play i.e crysis high setting 1280x1024 no aa 25-30 fps, bioshock high settings 30-35, settlers:rise of an empire aa on high 1680x1050 high settings between 30-35 fps

seen youtube videos bioshock on an hd4870x2 100fps +, settlers 200fps+, crysis very high 1680x1050 no aa 40-45fps+

 

[lee2008]

???????????? any ideas

 

[Amg]

might be a faulty psu ?

 

[aevm]

Take a look at this thread. You guys might have the same problem.
http://www.tomshardware.com/forum/256418-33-4870x2-performing-slowly#t1878740