I wrote above that when I reset my CMOS settings to default the system would not boot because it got stuck at verifying DMI pool. I also wrote that this was because the drive settings reverted to IDE instead of AHCI so the system could no longer see the drives and the DMI data was on a disc file so that was the problem. Well I was never quite happy with that explanation so I have looked further.
I was right about the IDE/AHCI thing but wrong about the disk file.
First off DMI is a bit wrong as it has been replaced by CIM anyway, what the system means is SMBIOS data pool. The SMBIOS gathers system configuration data during a boot and makes it available to an OS by putting it in a CIM formatted table and storing that near the top of the first 4MB of memory before handing control to the OS.
My BIOS does that thoroughly ONCE and stores the table in CMOS, on the next boot it just dose a quick verify of the data it has in CMOS and if all is well passes the CMOS data to the OS.
My problem was because of the IDE/AHCI mismatch. The main BIOS had reverted to IDE but the SMBIOS was still trying to get device information from an AHCI drive, which it never could, so I got stuck at verifying DMI pool. The simple solution is to do a CMOS reset which clears the DMI pool and forces the SMBIOS to do a rescan using BIOS settings.
Or just change the IDE/AHCI settings manually which is what I did 😂
There is much more to the SMBIOS data and configuration mismatch problems but I am tired of typing 😀
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