Is This GPU Artifacting?

Jun 18, 2018
Hi there,
First of all, sorry for bad english.
So, I need help to find out what actually happened to my computer. This is my spec;

Motherboard: MSI 990FXA-GD65
Processor: AMD Phenom(tm) II X6 1090T Processor (6 CPUs), ~3.2GHz
Memory: 8192MB RAM
Display Card: NVIDIA GeForce GTX 680

There's no problem browsing, watching youtube, editing some videos on premiere. But when I want to do some gaming, the problem occur.

Lets use fallout 4 for example. Still normal from the beginning until the loading screen (image below)

But as soon as the game starts, it looks like this (video below)

And when I do some benchmark with heaven benchmark this is what happened.

Directx 11, lots of triangle shape stretch like spikes (image below)

When I set it on directx 9, the spikes gone, but there's a lot of black squares (image below)

I already downclock the core and the memory to the max with MSI Afterburner, and the result still the same.
Please help me figure out what is happening to my PC, and if there's a way to fix it, I would be thankful.

Thank you...