Removing power causes "Devices Changed or CMOS cleared. Please enter setup..." screen.

Dec 3, 2018
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Specs:

MSI B350 PC MATE MOBO

16GB (2x8GB) T-Force Night Hawk DDR4 RAM (I can't remember exactly which speed)

Ryzen 5 1600

Radeon RX 580

Crucial MX300 m.2 SSD

Random HDD

Issue:

Whenever I disconnect the PC from a power source (removing the power cord), leave it unplugged for a while, and then start it back up, I will run into the "Devices changed (CPU or Memory) or CMOS have been Cleared. Please enter Setup to configure your system" screen. From this screen, I am perfectly capable of using any of the options shown and quickly loading into Windows 10, at which point everything works perfectly (except for the fact that I have to readjust the default RAM speed). This issue does not happen if I leave the PC plugged in and the power switch enabled.

So, naturally, I could either just leave it plugged in all the time or press the correct key and be done with it... but this isn't my PC and the owner isn't nearly as computer savvy as I am. I have no intention of giving it back to him in this state.

Thoughts:

I suspect that this might be a CMOS battery issue, but one thing makes me second-guess myself and that is the fact that, as you can see in the linked image, it gives me the option to load my saved overclock profile. I would think that, if the CMOS battery were failing, the saved profile would be lost with the rest of the saved BIOS settings.



Things I've tested:

I've left the computer powered off, but plugged in. No problems.

Unplugged for a few minutes. No problems.

Unplugged for an hour+, problem.

Memory Test: No apparent RAM issues.

Background:

I originally built this PC a little over a year ago. The first time I built it, I used a Corsair CX 450W power supply and, going by the reviews, I suspect that it started to fail. Either that, or something went wrong with the motherboard. In any case, one day the owner turned it on and it would not display any video (or POST, as far as I could tell). I RMA'd the board, rebuilt it, and it powered on for a second and then never powered on again (another reason I suspected the power supply to be bad. I RMA'd the motherboard one more time, rebuilt it with an EVGA 500w power supply and it powered on, but would not detect the SSD (this is also the first time I received the screen from the above linked image). I was eventually able to get it to try to boot into the Windows 7 install, but it would always blue screen after a long windows 7 startup (never actually getting into Windows 7). Windows 7 repairs failed, so I went nuclear and did a fresh Windows 10 install, at which point it loaded into Windows 10 and appears to be running perfectly while plugged in and powered on. This brings us to the current issue.



Any thoughts or suggestions? Thanks!