Did you know the 2nd bathch of Spice calculators are more accurate?

[brouhaha]

(05-19-2023 08:08 AM)J-F Garnier Wrote:  BTW, I didn't know that the 38E and 38C have different firmware, contrary to the 33E/33C.

The 33E and 33C have different firmware. They share the same CPU (1820-2105), so the first 1K of microcode is identical, and is mostly the arithmetic routines. The next 512 words are in different ROM chips, but have identical content (addresses octal 2000 to 2777). Because the ROM chips store 1K or more, they couldn't use the same chips for that region. The rest of the microcode is similar, but not identical. I haven't yet analyzed all of the changes, but they added detection for "Pr Error", so I expect they must have added use of a cold-start constant in RAM somewhere. There are some changes to the init routine starting at octal 3002, amd new code starting at 7000 does most of the work.

The 38E and 38C microcode are much different. Both ROM and RAM are substantially rearranged. It's possible that much of the code is actually the same, but because everything moved around, it's not trivial to discern.