Question R9 5900X + 6800XT rebooting randomly during gaming sessions


Nov 27, 2012
Ryzen9 5900X + Noctua NH-D15S on a ASUS Rog B550-F Gaming Wifi Mobo, 32 GB (2x16GB) DDR4 3600 Mhz Trident Z RGB, 1 TB PCIex4 SSD + 4 TB WD HD Sata, ASUS TUF RX 6800XT GPU. No overclock, beside DOCP for memory and PBO on default in Bios.
Case is Phanteks P400A (3 fans on the front as intake, 1 fan on rear panel as exhaust). PSU is Fractal Design Ion+ 860W 80+ Patinum.

Problem: in graphically intensive games, I expect random machine reboots (every 20-30 mins in Horizon ZD, every 30-45 mins in CyberPunk 2077): no BSOD, nothing logged in the Event logs (except that the reboot was not scheduled - duh Windows!), just a black screen, a series of audio "clicks" and a reboot with the video outputs dead until I manually shut down and restart the machine... What is strange is that the machine is rock solid in other, less intensive I guess, games: Genshin Impact, Lost Ark RU...

I ran all sorts of benchmark to try to pinpoint the problem, but everything is super stable for hours (Prime 95, memtest,...). Even the detailled logging in HWinfo64 during a session that ended up in a crash did not show (to my eyes) anything abnormal... I am at a loss there.