Ok, so.....
- Desoldered the old dead Dallas RTC chip with solder sucker, solder wick and flux
- Cleaned off the flux with Flux-Off
- Soldered on a DIP socket
- Inserted new 2022 Dallas RTC chip into the socket
- Powered back on
Noone was more surprised than me (given my ropey soldering skills) when it booted up and successfully saved the new 2022 date settings 😀 !
Only the corners of a couple of PCI and ISA slots were harmed in this ham-fisted effort - 🤣
It now reliably correctly recognises the Am5x86-P75 again.
The back-plate mounted CF IDE emulator is recognised (once I found a jumper and set it as the Master) since it actually remembers the BIOS settings changes I make.
So.....
The only remaining issue is that both the DOS 6.22 disc sets that I have seem faulty so I can't install DOS 🙁
I've tried two separate floppy drives, so assuming they're both not faulty then the issue seems to be the floppies themselves.
Does anyone have a known-good set of DOS 6.22 floppies I can borrow ? (hardly piracy as I already own two copies of DOS 6.22 😉 )