OCCT

OCCT is a free overclocking and testing tool for hardware units ram, cpu, gpu, power.

 
 Test every component of your PC using 6 powerful, efficient tests!  CPU, Memory, GPU, VRAM, Power supplies, every critical component can be tested.
 
 View inside your computer using the built-in monitoring and system information engine based on OCCT's award-winning HwInfo64 engine.
 
 OCCT's CPU test is the most advanced test out there.  It can detect stability issues in seconds, perform per-core testing, and allows you to customize the instruction set and data size used.  Are you an expert?  Search elsewhere.
 
 Need to test GPUs without a screen, like in your crypto mining farm?  OCCT has the only 3D stress tester that works without the screen attached.  You can also limit the 3D test load to stay below the limits of your own GPU.