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The "Firmware" tab of the DM-15CC Website provides downloads for the following HP 15C versions:

DM-15CC firmware 'vanilla'

DM-15CC firmware 'mem80' with extended memory

DM-15CC firmware 'mem1b' with even more memory *

With the caveat on the last being:

" * with the mem1b version you must not make more than 999 pgm steps... the unpredictable may happen."

I would assume that the 'mem80' version has 128 (0x80) pool registers. But it is not clear about how much extended memory the 'mem1b' patch version provides.

In an old thread, Eric and HrastProgrammer made it clear that 128 was the upper limit of the number of pool registers available without the need for extensive patching to the ROM. But, given the caveat for the 'mem1b' version, we can assume that it supports at least 143 pool registers.

Has anyone successfully applied any of the alternate ROMs? I would be curious to know how far Michael was able to extend the DM-15CC's memory.

Mark Hardman

Edited: 15 Feb 2012, 3:02 p.m.

I suspect that mem1b would have 229 pool registers (0x100 - 0x1b), but I haven't tried it.

The original HP15C has covered memory range c0-ff which means the area of 64 registers (note that the two or so registers in lower part of memory are counted to register pool, but just concentrate on this part of memory).

The mem80 extends this to 80-ff range i.e. 128 registers.

Similar situation with mem1c extends the range to 1c-ff i.e. 228 registers. I don't remember it exactly ... but I think the area is somewhat shrunk when the integration or solve is activated ... so the base for temporary registers in such case starts at 20h not 1c. It means there will be 4 less registers then could be expected.

Does it mean that there is a possibility to upgrade the total amount of registers of HP 15C Limited Edition?


A possibility, perhaps. It will depend on a few unknowns. How HP has allocated the 2kb of non-volatile RAM the 15C LE's CPU has. Is there "free" space the beside the current registers e.g.?

An alternative path to achieving something similar might be to port an older version of nonpareil to the hardware. At least, it would be worthwhile considering this option as well.

- Pauli