Here is my current clock speeds with the corresponding BIOS settings
A8-3870K @ 3.0 GHz (undervolted @ 1.25 Vcore)
HD 6550D @ 757 MHz (stock is 600 MHz)
ASRock A75 Pro4-M (BIOS v1.50)
G. Skill Ripjaws X 4GBx2 DDR3 1866
CPU NB Frequency Multiplier: 900 MHz
CPU NB/GFX Voltage: 1.200 V
GFX Engine Clock: 757 MHz
DRAM Frequency: DDR3 1866
DRAM voltage: 1.500 V
APU PCI-E Voltage VDDP: 1.208 V (min: 1.208 V / max: 1.800 V)
APU DRAM PHY Voltage DDR: 1.200 V (min: 1.200 V / max: 1.400 V)
CPU Load Line Calibration: Auto
SB Voltage: Auto
It is stable in gaming, video encoding, and watching HD movies
My problem is when I try to set the GFX Engine Clock (HD 6550D) to 800 MHz or higher while retaining all other BIOS settings, my PC crashes when playing HD movies. But it is stable in gaming
I tried increasing the CPU NB/GFX Voltage to 1.325 V but the problem still persists. I returned CPU NB/GFX Voltage to 1.200 V then increased APU PCI-E Voltage VDDP to ~1.300 V but my PC still crashes when playing HD movies
I don't know what to do anymore. I really want to make 800 MHz stable and hit higher speeds on HD 6550D. I have seen lots of review sites being able to reach 800 MHz to 900 MHz. The review sites didn't go into specifics, they just indicated in their reviews that they set the IGP voltage to ~1.3 V.
I'm confused with my board's BIOS settings. I don't know which one is for the "IGP voltage"
Just been working my overclock on the 3870K, I have a different mobo than you. This said the nb voltage you need to tweak to improve Graphics performance is 1.2volts as stock standard. I have raised mine to 1.25volts and run my GPU at 800Mhz no bother. Had 960Mhz before but lowered it in case it was impacting on my CPU attempts. Now settled on 3.6Ghz overclock, well stable. Think you may have raised the nb voltage just too much. Try 1.25v first and see if that helps your blue-ray playback. Am gonna be doing blue ray, just not connected the drive yet. Too much BF3 so far, medium settings. Plays well, looks fuckin fantastic.