What causes "Overclocking failure" reboot?

[BrandonCSLC]

Fx 8320 @ 4.2GHz
Asus M5A99FX Pro.
Corsair H60 liquid cooler
GSkill 1600MHz DDR3 (16gb)

Followed an overclocking guide found on the internet along with guidance from several threads in TH. Tested in Prime95 for an hour with temps stable at 55C while under heavy load. Normal operating temps range from 25-40C. Everything was running fine for several weeks. Two days ago while playing a game the computer shut down and reset to a screen that said "Overclocking failure. Press F1 to enter setup."

When I pressed F1 it sent me to Bios where it had reset to factory defaults.
I repeated the process to overclock the CPU. This time I have it set at 4.0GHz and everything seems to be fine again. What happened? Is 4.2 mire than my CPU can handle.

Also the temps at the time of the incident where fine. Around 40C while gaming on the CPU and the socket temp was about 50C.

 

[4Ryan6]

So... Returned bus speed to 200Mhz and set the multiplier to 21.0. Ht link 2600 and NB at 2200. Ram frequency at 1600 and CPU voltage at 1.32V. Still reading 1.308V while idle and 1.284 under load. WTF?

Found the reason for the voltage drops when running applications and Prime95. LLC was set to high which only increases voltage by 50% when demand is needed Ultra High is 75% and Extreme is 100%. Sett LLC to Ultra High and now the voltage is locked at 1.32v for a 4.2GHz overclock on my FX8320. Things seem to be stable. No stutters while gaming and reasonable temps. More testing will come before I increase to 4.3Ghz. Trying to shoot for 4.4.

Good!

 

[BrandonCSLC]

That multiplier.... good stuff! What do you look for when finding a stable voltage?

 

[4Ryan6]

That multiplier.... good stuff! What do you look for when finding a stable voltage?

http://www.tomshardware.com/forum/id-2345618/reaching-cpu-overclocking-stability.html

 

[BrandonCSLC]

Woe is me! Looks like I reached a thermal wall with my O.C. 4.2GHz @ 1.34v. Idle temps at 26-28c. While gaming the CPU hits 50C but the socket temps reach mid to high 60c. Running Prime95 for 20 minutes causes cpu and socket to go into the 70's and it throttles back the core frequency. Lack of airflow in the case is causing the issue. Just ordered a Phanteks full ATX case. If that does not work than I will replace the H60 with an H100.

The difference in performance between 3.5 and 4.2GHz is night and day. I think this chip will be amazing at 4.4 or 4.5GHz. Could have bought an intel with the money I am dumping into this but... this is way more fun!