CPU throttling on low temps

[mangopearapples]

CPU: AMD FX 8120 @ 3.1GHz (stock)
MOBO: Asus M5A78L-M/USB3

I have all of the power saving settings turned off, i.e. Cool n Quite, Turbo Core.

I tried overclocking at first and got to 4.0GHz without any crashing however I noticed that my core voltage and clock speeds would drop to 0.9v and 1.4GHz when running Prime95!
It's definitely not my CPU temps because they never go above 40 degrees C (Corsair H80i).
When this happened, I lowered clock speeds and voltages and kept checking.

The same problem kept occurring so I eventually just put everything back to stock (except cool n quite and turbo core). So clock speeds back to 3.1GHz and voltage to auto (which gives me about 1.32v).
But the same problem now occurs at stock speeds and voltages. Wtf!

I don't think it's my MOSFETs overheating because I looked at the data sheet and it says it can operate at 175 degrees C.

Here is a graph of my voltage and clock speed over time:

My windows settings are set to Min: 100% and Max: 100%.

How can I fix this?

Thanks.

 

[bignastyid]

The VRMs on that board a too weak and likely to cause throttling on a 125w cpu even at stock settings. This is a common problem with the 760g and many 970 boards that use 3+1 and 4+1 VRM setups. Sometimes adding heatsinks to the VRMs and making sure they get airflow will help, but the only true fix is a better motherboard.

 

[Supahos]

Yep I'll bet ya anything it's the board for the same reason listed above. My nephew has same board and an 8320, we managed to keep it from throttling while gaming by just undervolting and leaving speed alone, it will still throttle running prime however

 

[mangopearapples]

Yup it was the VRMs... Placing a fan in front of the open case actually helped with the throttling. Thanks for the replies and info.