Supermicro X11SSZ-TLN4F fails to reboot, and BIOS update woes

A system which consistently fails to power-cycle. Really fun, especially when it generally sits in a corner not hooked up to a keyboard and/or monitor.

Debugging this issue, I discover the system has no trouble rebooting if I hit ctrl+alt+del before OS boots. But once it has left the BIOS sphere and booted something, be it FreeBSD or FreeDOS, telling it to reboot would make it try to reboot but fail to do anything after the “shutdown”. It would be powered on, fans running, but no POST, no VGA output, and the “power on LED” on the mainboard would not light up. No error beeps or codes.

I’ll try to upgrade BIOS to solve this as I’m on 1.0b and latest available is 2.0a, but doing that requires a reboot to make mainboard enter FLASH/UPDATE mode, which is where it once again fails and can’t get to the point where it actually flashes the BIOS.

I also had some trouble booting the FreeDOS USB stick, I suspect this has something to do with my UEFI/LEGACY settings. Simply switching to legacy or legacy+UEFI boot mode didn’t solve it, but after loading optimized defaults (or resetting BIOS by plucking out the battery, if that’s your thing) it would boot FreeDOS.

But back to actually getting to upgrade the BIOS when upgrading BIOS requires a successful reboot; which this mainboard can’t do, and is the reason I’m upgrading the BIOS in the first place:

After looking through the manual, I discover there’s a jumper that can be changed to force mainboard into FLASH/UPDATE mode from the get-go. I also discover this can be configured in the BIOS screen, so I opt for the second approach and try to upgrade the BIOS again. (The setting is located at: Advanced -> PCH-FW Configuration -> Me FW Image Re-Flash; set it to Enabled)

This time, it successfully flashed the BIOS at least. And the aforementioned Re-Flash setting is back to disabled. But the problem persists, and I’ll keep debugging it.