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Low -12 volts on Asus motherboard

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December 21, 2009 11:42:22 PM

I am running an Asus M4A785TD-V EVO motherboard with AMD Phenom II 955x4 3.2 Ghz processor, 4Gb Corsair DDR3 1066 memory and a BeQuiet! 650 power supply, and running 64-bit Windows 7. BIOS set to automatic. The system is inherently ustable. It has no specific one problem, but the system variously hangs, runs slowly, parts of the operating system stop working, the screen goes blank, memory errors are displayed, etc. Memory tested ok. SANDRA showed that the -12 volt supply was only -8.91 volts. All other voltages were fine. I replaced the power supply. Still - 8.91 volts. I then tested the new power supply in my old computer and SANDRA showed -12.01. I concluded that the problem was the motherboard so replaced that. However, new motherboard also showed -8.91 volts on the -12 volt supply, and has the same instabiltiy problems. Can it be that both motherboards have the same fault, or am I missing something?
a b V Motherboard
December 22, 2009 1:40:51 AM

Probobly nothing running thats using (-)12v, it also depends on Where the program used is measuring the voltage at. If you pull up the program you're using to measure voltage and run a load like processor benchmark you might see a voltage change. The monitoring program would have to be set to continuously measure.
Recommend you set ram voltage to manufacturer spec's and see how stable system is.
December 22, 2009 2:09:58 AM

Nothing will run at that voltage......it sounds like an error with whatever is monitoring the voltage.....
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December 22, 2009 10:07:22 PM

roonj said:
Probobly nothing running thats using (-)12v, it also depends on Where the program used is measuring the voltage at. If you pull up the program you're using to measure voltage and run a load like processor benchmark you might see a voltage change. The monitoring program would have to be set to continuously measure.
Recommend you set ram voltage to manufacturer spec's and see how stable system is.



Thank you. Changing the RAM voltage from auto to 1.5v (the RAM specifiation) in the BIOS appears to have made the system stable with no hangs or other mysterious events at all. The voltage is still a mystery but the computer now "feels" stable, if you know what I mean. I have been encouraged by the improvement to install the graphics card! Your help is much appreciated. Thank you.
a b Ĉ ASUS
a b ) Power supply
a b V Motherboard
December 22, 2009 10:32:50 PM

Disregard the -12 V reading.
Modern systems do not use the -12V, and most monitoring programs do not display it correctly.

Should look at +3.3, +5, +12, Vcore and Ram voltages. As roonj stated run program like Prime95 to place a load (primarily on +12V) an look aqt the decrease.
January 6, 2010 7:59:46 PM

Thank you all. The system is getting better as time goes on and further tweaks are made. I am coming round to the conclusion that the fundamental issue is probably with 64 bit Windows 7 and its interaction with other programs on start up. Disabling most of these helps, and I think that telling Windows to load using all four processor cores has also helped. That said, I still experience occasional memory errors, particularly when logging on a user after initial startup has finished.
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