Weird CPU Voltage on the -12V Line

[Yasashii]

I've been fighting a DPC latency problem with my system (causing poor performance, audio pops and clicks, sudden freezes in games and stuttering in video playback). I've done a lot of stuff to try and diagnose and fix it to no avail so far. While researching potential overheating problems I've noticed that the voltages on my CPU might very well have been the problem all along. This is what popped up in the CPUID HWMonitor:

 

The voltages on the -12V line are actually -6.2V.

Is this an actual problem or is it actually correct for a reason I may not be aware of? If it's a problem, is it more likely to be caused by the PSU, the motherboard or the CPU itself? Is there a fix/dirty workaround for it that doesn't involve buying expensive new parts for a system that isn't really worth it?

 

System specs:

• CPU
  AMD Athlon 7850 Black Edition (2x 2.8GHz)
• Motherboard
  ASUS M3N78-VM
• RAM
  8GB DDR2 5-5-5-15 @400MHz (slightly overclocked)
• GPU
  ASUS GeForce 9800 GT (1GB GDDR3)
• Storage
  1TB Seagate HDD
• PSU
  OCZ ModXStream Pro 600W
• Cooling
  Stock
• Sound
  ASUS Xonar DX 7.1
• Operating System
  Windows 7 Ultimate SP1 x64

[vanished]

First of all, that's not the CPU voltage   CPU will be in the 1 - 1.5 range.

 

Second, in some cases, software measurements of voltage are insanely off to the point where they're meaningless.  I suspect this may be one of those cases.

 

As for the latency problem you mentioned, usually it's related to some driver.  Try disabling them all one by one to see if one of them fixes it.

[Mira Yurizaki]

The ATX spec requires a -12V line, due to some hardware needing a negative reference voltage like sound cards, RS-232 ports, or PCI devices.

 

So nothing to worry about if you don't actually use those.

[Mr.Cunt]

most likely its software/sensing problem. that rail should be fine, but if i were u, i would just in case measure it with multimeter manually. 

 

to measure it:

1. unplug your 24pin(preferably other cables too, but it should be fine even if you leave them in)

2. connect multimeter to blue and black wires (all black wires are - , it dosent matter to which one)

3. short out green and black wire (to turn it on)

4. read the number off multimeter

 

 

[Cracklingice]

I don't think I've ever seen a -12v line actually display -12v.

[Yasashii]

Well, it seems that it's unlikely to be the problem. Since I'm out of ideas at this point I will be posting a full detailed thread about my problem shortly.

[mariushm]

-12v was implemented in computer power supplies in the time of ISA slots, where modems and sound cards  needed a -12v and a +12v for the operational amplifiers they often used.

 

Modern computers have -12v only on PCI slots and on serial ports. Most computers these days don't even have PCI slots and most PCI cards don't use the -12v rail so they don't care if it's missing. Pretty much only PCI sound cards (very few) and serial port cards/modems on PCI may use -12v

 

Serial ports represent digital 1s as anything above around -8v .. so -8 to -12v it's the same thing from the hardware's point of view.

A lot of the modern hardware that works with serial ports even considers a digital 1 anything below around -5v to -6v in order to make it very easy for the chip to invert the signals in a very simple and cheap way and produce TTL signals (5v for digital 1s , 0v for digital 0s)

 

Because the -12v is almost not used, most power supplies don't bother regulating the output as accurate as the other output voltages... they often use a rudimentary way of regulating the output. Basically, with nothing taking power from that -12v wire, the power supply will output some crappy voltage .. as I said something between -8 and -12v but typically around -11v .. -10v

As soon as something starts consuming some power, the voltage regulator producing that -12v will react and bring that voltage more in line to what's ideal, something close to -12v