BIOS OC is unstable, same OC in Intel XTU is stable?

[LeatherKnot]

I have an ASRock Extreme4 x99 motherboard. And an Intel i7-5820k, with a Cryorig H5 Ultimate cooling it.
Using the Intel Extreme Tuning Utility to set OC the CPU and AIDA64 as a stress test.

Clock speed: 4.4Ghz

Voltage: 1.2002v

Temperature: ~74C

I ran this setup successfully for 4 hours before deeming it stable.

Then I went into the bios to make this OC permanent, using the exact same settings.
However after applying these settings the computer freezes during startup and has to be powered off by holding the power button

Short and Sweet: How come my OC is stable in Intel XTU but freezes during boot-up when OC applied in BIOS?

Intel XTU settings, AIDA 64 Stress Test

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BIOS CPU Speed OC

BIOS CPU Voltage

 

[Tradesman1]

Intel may be making some additional changes, might try raising the vCore, (CPU voltage) up just a couple ticks, maybe add + 0.04

 

[AdmiralDonut]

One of the major issues with that board is that the voltages you see in BIOS are not accurate. It is a well known issue amongst ASRock owners, but for more details see here:

http://www.overclock.net/t/1360404/asrock-z77-series-vcore-reading

Please be very, VERY careful when changing voltages on that board, or you may end up frying the CPU/motherboard.

EDIT: And yes this DOES affect the X99 boards as well as the Z77 boards.