[totalz]

PCI-E is explicitly set to 100MHz in bios, still no good.

PSU should be powerful enough, but I cannot get any reading from the sensor about +12V!

Voltage: cpu=1.05V , ram=1.6V , others=default

Bus: 170
Multipler: x20
QPI: x44
SPD: x10

 

[Blameless]

Lower the QPI multiplier more.

Also, really test the stability of the CPU OC.

 

[chadamir]

If you're sure the cpu is stable then try increasing the ioh/ich.

 

[totalz]

Actually to my surprise, one particular screen saver will restart my PC after i7 is OCed...

And that's the cause of unstable!

 

[TurboTurtle]

Only 1.05v at 3.4?

Are you sure the overclock is stable with that low of a Vcore? See how long it lasts in any Prime95 test.

 

[totalz]

I tested with OCCT to make sure all 8 threads are used...