Finally an update to this topic!
I did my homework and replaced the Varta 3 battery with a somewhat more modern NiMH counterpart. In fact the old NiCd happily charged up to 3.6V on my hobby charger 😀
Also had to resolder the ceramic decoupling capacitors sitting underneath the CPU package since those where pushing against the CPU itself. Most likely this was a tight fit with the early Gold heatspreader P90 CPU and the somewhat later revision P100 I have in possession protrudes just a tiny bit more.
Now on to my POST issues ->
With no memory installed or in the wrong memory bank/order I get PC speaker beeps with POST code:
C1BE (which indicates something about memory so fair enough)
With SIMM installed (in the assumed correct bank/order) - I tried several combos with the SIMMs I have - I get no beeps but the POST code:
060A (06 is Award BIOS reserved)
Edit: This is 0B 0A (as concluded further down in this thread) 😊
I have been searching for the 060A (0B 0A) POST code but to no avail. Anyone else out there who have observed this 🤔
ROM checksum error maybe?
It is definitely not a PNP BIOS, it reads the following:
Any feedback is much appreciated! Cheers 🍻