graphics card - What can cause my PC's voltages to be off?

I have recently started experiencing very strange issues on my self-built PC system. Although the system is still very speedy, it's very fluctuating now. This is most notable when using graphically intense applications.

To resolve it I tried ran some stress tests on CPU, RAM and GPU. All this showed is that those components are actually functioning quite good. (Cooling is also good, 100% CPU for 20 minutes resulted in a stable 48 Celsius in temperature. AFAIK until it goes near 70 it should be pretty.)

I also think I can exclude my HDD/SSD from being the problem, because my system boots in about 10 seconds.

But what caught my eye is my very odd voltages. The information from OCCT shows:

╔═════════════╦════════╦════════╦════════╗
║ Sensor Name ║ Value  ║  Min   ║  Max   ║
╠═════════════╬════════╬════════╬════════╣
║ CPU VCORE   ║  1.43V ║  1.39V ║  1.43V ║
║ VIN 1       ║  1.5V  ║  1.5V  ║  1.5V  ║
║ +3.3V       ║  2.02V ║  2.02V ║  2.02V ║
║ +5V         ║  3.39V ║  3.37V ║  3.39V ║
║ +12V        ║  8.02V ║  8.02V ║  8.06V ║
║ -12V        ║ -6.34V ║ -8.11V ║ -6.14V ║
║ -5V         ║ -8.88V ║ -8.88V ║ -8.88V ║
║ +5V VCCH    ║  2.78V ║  2.78V ║  2.78V ║
║ VBAT        ║  1.61V ║  1.61V ║  1.61V ║
║ VIN0        ║  0.82V ║  0.82V ║  0.82V ║
╚═════════════╩════════╩════════╩════════╝

Now I'm no expert, but this seems to me like something is very much wrong. And could be causing all sorts of instabilities. It even makes me wonder why my system hasn't exploded altogether.

My guess is that there can be 3 possible explanations for this problem:

• Broken power supply
• Broken motherboard
• Wrong configuration (software or hardware)

Some specs about my system:

• MOBO: Gigabyte GA-990FXA-UD7
• CPU: AMD Phenom II X4 965 Black Edition
• GPU: Sapphire 11199-19-20G AMD Radeon HD 7870 Dual-X OC
• RAM: Kingston ValueRAM KVR1333D3N9K2/8G
• PWR: Corsair Builder CX500 V2

Symptoms on the software side are that sometimes performance is unstable. For example in the Box2D testbed, I often times run at 60FPS capped. While other times it barely reaches 1-5FPS in the same tests.

What can be causing this problem? And more importantly, how do I fix it?

It seems pretty clear that the software you are using to report voltages doesn't understand your hardware. Use the software offered by your motherboard manufacturer.

In addition to the accepted answer, here's some background info on how hardware monitoring works (I'm not a electronics specialist nor an electrician, all of this is based on a datasheet I read a while ago about a hardware monitoring chip, they are present on almost all boards and also take care of stuff like fan control) :

The ADC on the hardware monitoring chip only accepts small voltages, the maximum is probably around 3,3 V, so to measure higher voltages like 12 V they have to be stepped-down using resistors, and then the software should do the appropriate math to get the correct value based on the resistor's values.

Easy example :

You need to measure 10V, but your ADC can take 10V at max, since you also need to be able to measure more than 10V, you use resistors to lower that voltage, let's say the resistors divide the voltages by 2, so your ADC sees only 5V even though the real voltage is 10V, and your software should account for that and do the correct math, which means real voltage = ADC voltage * 2.

The OCCT software just doesn't do that calculation right and displays values that are either off of are the raw ADC values without any corrections, so that's why they seem strange.

And if those voltages were real your machine won't even boot, 8V on the 12V rail is way too low.