HP-15C expanded memory firmware: problems with matrix larger than 8x8

[brouhaha]

(07-06-2024 04:46 PM)Giorgio Wrote:  Thanks for explaining the source. I was unaware of the provenance of the 15C LE and 15C CE firmware, and had never checked it myself.

Someday perhpas I'll explain the precise detials of how the Nonpareil modified ROM images came about, but not today. The only functional difference was the shifted "r" in "running". The remaining differences were for identification, and to make the checksum for self-test come out right. At the time I didn't know which words of ROM in the Voyager claculators were the checksum adjustment, so I just added a second adjustment. More recently, I've identified (to a very high degree of confidence) whcih words of ROM were HP's checksum adjustments.