Modern motherboard firmwares (#BIOS for us oldtimers) are outright awful. Toggling a single option X on/off isn't necessarily binary. Enabling option X might enable other option Y (and maybe more) which will remain enabled even if you disable X again.
This makes it extremely difficult to do binary search on situations where some firmware option causes you trouble.
I was bit by this earlier today when I enabled AMD Precision Boost Overdrive on an AM4 system. The system would start to fail compile tasks randomly (and #Prime95 within second) when PBO was enabled. Confusingly disabling PBO did not result in a working system, but the system kept crashing. I updated the firmware to the latest version and the system became stable again. "Great, #AGESA update must've fixed the stability issue!", I naively thought. So I enabled PBO, system kept crashing, I disabled PBO, system kept crashing. Frustration ensued.
"When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth". Enabling PBO pulls some other options which cause the stability issue, and disabling PBO doesn't disable them.
Sure enough, resetting BIOS to default, then enabling everything but PBO resulted in a stable system that is able to run Prime95 for hours. While it might be possible to figure out what this "extra" option causing the instability actually is, at this stage I was happy to just have a working system. It won't touch PBO on this box ever again.
