Peculiarities in HP supplied S/SX and G/GX ROM dumps

[Jonathan Busby]

I've been dumping some ROM's lately for some code that I've written and I've noticed something strange. Some ( or all? ) of the HP supplied HP48-S/SX and HP48-G/GX ROM dumps on http://www.hpcalc.org contain what looks to be garbage starting around 0x0100h ( in nibbles ). The ROM dumper that I've written first de-configures ports 1 and 2 and IRAM and moves them to the lower 256KiB of memory. After that, the code dumps the upper 256KiB of ROM and then it re-configures the aforementioned memory controllers back to their default locations but then moves the hardware regs to the upper 256KiB and dumps the lower 256KiB of ROM starting at address 0. My guess is that whomever wrote the code to dump the ROM for the dumps that are available on http://www.hpcalc.org forgot to re-configure the hardware regs which start at 0x0100h, and subsequently "dumped" the reg contents, as, it's supposed to be all zeros there, for at least 64 nibbles.

It's just curious as the dumps are supposed to be provided by HP.

Any thoughts?

Jonathan