Casio CFX-9850GB Plus 32KB WE (White Edition): 64KByte "upgrade" reconfiguration

[Mark]

You're welcome, Jose :-)

I was in a hurry when I wrote my first reply ; you're right, the CFX-9970GT seems to be mostly identical from a software point of view. I just did another self-test on my 9990GT :
- The model code is ZX936 (same as yours).
- The RAM test displays "RAMSIZE 128K byte"
- The next 2 lines display "RAM OK (64)" and "RAMaddress FFFF".

I may be wrong, but I suppose that :
- The firmware surely has been designed to manage a 128K RAM.
- If the machine is configured for 64K, the self-test only covers the 64K half it can access.
It will be interesting, shall I eventually succeed in configuring my machine for 128K, to check if the test actually runs through the whole 128K space.

ROM side :
- My machine displays "4Mbit ROM Ver.2.0" and "8MbitROM Ver.2.0"

I get the very same forensics test result, which means that the math routines are the same. I'd also say that the processor core is the same, simply because of the high costs usually associated to porting whatever software from a CPU architecture to a different one (costs mainly induced by the tests).

On the hardware side, I remember that it doesn't look the same as the CFX-9850GB, it is more complex : 6 LSI chips versus 4. I only opened it for a few minutes to check for corrosion, the day I got it for a few bucks. I suppose that the 9850 is a more integrated iteration of the same architecture...

A last note : the "HCD62121" reference puzzles me : In the last 40 years, each Hitachi custom LSI chip I encountered was labeled "HDxxxx" or "HDxxxxx" -but no HCDxxxx. Strange...
EDIT : I read the service manual... it could be the designation for Hitachi bare chips, to be mounted as "chip on board"... ?

Best regards,
Marc