Idea PC Crashes at the Arithmetics Test

Hi guys,
My pc crashes often while playing PC games. Usually it never crashes at Benchmarks exept at the Benchmark Catzilla. It allways Crashes at the (Raymarch Test/ Aritmethiks test)
I was able to exclude the Graphicscard as reason for the crashes (i barrowed it to one of my friends and everything was working just perfekt, and i already send it back, without successe)
Beside i had some crashes as well with only the Intel HD4600
I can also exclude overheating as well. I stressed my CPU and my graphicscard seperated at the same time, and got CPU temperatures over 90°C and GPU Temperatures over 80°C, and the PC didn´t crash.

So my question is, which part of the PC exept the GPU, is specially stressed in the Arithmetics (Raymarch Test), where the crashes apear usually?

Thanks for answers
Tilman


PC Hardware:
CPU : i5 4670K (no overclocking)
MB : d3hp Gigabyte z87 rev 1.0
RAM: 8GB 1866Mhz G.Skill Sniper elite
GPU: Palit Nvidia gtx 780 (no overclocking)