If you exceed the capacity of the PSU and trip one of the protection circuits, it should completely cut power. When that happened to me, it needed a power cycle before it would boot again. So I'd say that something goes wrong after the PSU. It could still be a voltage drop at the GPU (see other comment regarding cables). Maybe even just a driver/software issue.
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Ok, I didn't know that. Yeah, all my theory was based on wrong assumption. Thanks
No idea what your problem is. But I do know that GPU is sensitive to power requirements, specifically, is the GPU powered with three individual, separate pcie power cables? They cannot be daisy chained or shared. It should be three separate cables from the psu
yes, the all 3 separated cables are connected directly from the PSU :/
Found the issue while check if any video cable was bad. The GPU got very hot. As the drivers are not collecting temperature sensor from GPU, it was not visible for me. Putting all FAN on full power all the time was enough to keep GPU cold, no "power" fluctuation or computer crashes. As almost always, the problem is on the basics.
Thank you all.
I wouldn't expect that hardware to be able to use more than 1kW. Is the CPU or GPU overclocked?
Use a watt meter to check the load. Don't forget to take the power supply efficiency into account since it will be measuring input power. If the power supply is not overloaded, check the voltage rails with a multimeter while the PC is under heavy load. If the rails are all within tolerance, check the 12V rail with an oscilloscope and look for any dips or excessive ripple while the PC is under heavy load.
No overclocking, I assembly, bios default. Only tune was be more aggressive into fan to see if reduce the problem.... Thanks for the suggestions, I not capable to do that, but can bring to shop. But confirm that should not use more that 1KW was good, so my theory is broken :D