Black screen followed by pc freezing

[Iliasvela]

Here is exactly what happens randomly to my pc:
Screen goes black (there is also a white line just like old televisions while its going black), nothing happens for like 5 seconds... pc freezes (for example a song would keep playing normally for some time before the sound would freeze)

I saw another article and the person who had a similar problem said that he fixed it by increasing the RAM voltage by a tiny bit (from 1.2v to 1.26v) i have changed my RAM voltage to 1.21v but i would like to know why this happens

Here are my pcs specs:
i7 6700
Sapphire R9 390 Nitro
2x4gb Kingston HyperX Fury DDR4 @2400Mhz
ASRock Z170 Extreme4 BIOS Ver. P1.60
1TB WD HDD
Corsair RM750i 80+ Gold PSU

Also i have noticed that it happens while i am not playing games or using any heavy applications.

 

[zarsak]

Some higher frequency DDR4 RAM are rated to run @1.35v, so, according to this: http://wccftech.com/skylake-does-not-support-ddr3-damage-ddr3l-only/, you can safely go up to 1.35v on skylake.
Also, I've read MANY reviews about faulty z170 motherboard RAM slots. I would RMA the mobo or overvolt the ram @1.35v and see what happens.

EDIT: VCCIO/System Agent voltage are both also important for memory clocking. Since 2400MHz is above the standard clock, try setting 1.25V for system agent and 1.20V for VCCIO. These values should be enough to achieve 4 DIMM stability even at DDR4-3200.
Since you are using 2400MHz sticks and not 3200MHz I would lower those voltages a bit once I assured the whole system is stable enough.

Please let us know if this fixes the problem.