MSI B450 Gaming Pro Carbon AC - no POST after BIOS flashback

[DragonQ]

I have performed a BIOS flashback on a brand new MSI B450 Gaming Pro Carbon AC motherboard using the official instructions. It appears to work fine - the LED flashes for 5 minutes then stops, the motherboard resets itself and then just sits there doing nothing. The first time it did this I waited a good 10 minutes before powering it off and on.

Once I've power cycled the board, I am greeted with a "new CPU, configure BIOS" message. I go into the BIOS and do "save and reboot". Now the system refuses to POST at all and the CPU debug LED immediately comes on and stays on when I turn on the power. Clearing the CMOS doesn't help. The only way I can get back into the BIOS is to do a fresh BIOS flashback, but every time I do this, enter the BIOS and reboot, I get stuck with no POST, no monitor, no USB, nothing, and a red CPU debug LED.

I know the CPU (R5 3600) is fine because I tested it in another machine beforehand. Also, I have at least gotten to the BIOS a couple of times.

Any ideas?

 

[DragonQ]

Sounds weird, the fact you can actually get in to the BIOS and then errors on the next boot. Have you altered any settings in the BIOS while it was working the first time?

The first time I got to the BIOS I changed settings because I thought everything was fine. Other times I've gotten into the BIOS (i.e. immediately after flashes) I have just left it at default settings and it always fails to POST on subsequent boots. Even clearing CMOS doesn't help so I'm sure it's not a settings issue. It sounds like the BIOS is just bugged, despite the fact that the website says it supports Ryzen 3000 and isn't even a beta release.

I've also tried the older version 7B85v16 from March (release note just says "Support new upcoming AMD cpu") and that one doesn't POST at all.

 

[DragonQ]

You don't happen to have tried a single stick of RAM on first boot, and the subsequent boot after that?

I've done two Pro Carbon AC's in the past week, and three in total and I'm yet to have one that doesn't work.

My method for flashing was:

1.) Empty board, no CPU or RAM installed.
2.) Flash drive loaded with only one file MSI.ROM (http://download.msi.com/bos_exe/mb/7B85v17.zip)
3.) Flash board, power down system and unplug from the wall.
4.) Install CPU with cooler and RAM, plus GPU etc. (Slots 2 & 4 for RAM)
5.) Plug system back in with all Front Panel headers connected correctly.
6.) Turn on system, allow 15-40 seconds for first POST
7.) Enter BIOS via F1 message, and check all of the setting are as expected but not altering anything.
8.) Insert flash drive with Windows Installer, install Windows 10 1903.

That was it, has worked every time.

I did try moving the RAM sticks around and trying only one at a time, etc. but it didn't help. I seem to have made some progress though!

I tried flashing the older BIOS (v16) then once it had finished it just sat there confused. I then flashed the newer BIOS (v17) and it finished then booted straight to Windows! This is the first time it's done this, every other time I've flashed BIOS (v17) it's asked me to go into the BIOS.

I then rebooted and went into the BIOS, changed one random setting and did a "save and exit". The board was stuck again. I power cycled it and got back into Windows. I went back into the BIOS and confirmed the setting change had been remembered. I then enabled XMP, saved and exited, and it was stuck again. Power cycled it and it got back into Windows.

In summary, it seems like going into (or more specifically, leaving) the BIOS results in the board getting stuck. Flashing the older BIOS first allowed the board to boot without needing to go into the BIOS, hence it seems to work.

EDIT: So far, every single reboot whilst trying to install a fresh copy of Windows has failed. Every time I have to press the reset button on the case to complete the reboot.

2. Disconnect case's reset button from motherboard pins.

I might try this because (a) I've heard that trick before, (b) it definitely seems to have issues restarting from the BIOS.

 

[DragonQ]

Still not 100% fine but so far every time it fails to POST it works after 1 or 2 resets. Definitely not ideal but usable for now.

 

[DragonQ]

What is you RAM set at? Freq, Timings etc.?

Irrelevant. Happens at stock or XMP.

 

[DragonQ]

Current status is the PC struggles to POST. This morning it took about 15 resets to get it to boot. Once it's booted, it's fine and can be restarted no problem too. I've given up reflashing it now, tried it 5 times and it makes no difference. The flash is clearly working fine, the UEFI is just screwy.

The beta v18.1 UEFI seems to fix the boot issue for everyone that tried it on Reddit, but also seems to mess up idle voltages. Maybe that'll be fixed once v18.x is actually released.