What has the DM41 extra over the HP42s?

[Thomas Okken]

Free42 has most of the functions of the 41CX, the exceptions being the functions that deal with extended memory, the stop watch, and alarms. (CLRGX, GETKEYX, and the six indirect comparison functions X=NN? etc. are also missing but will be added in the next release.)

This means that Free42, and hence the DM42, will run most HP-41 user code software. That includes user code ROMs, which can be converted to raw files using the rom2raw program and imported.

What Free42, and hence the DM42, can not run is anything that involves HP-41 machine code, or that requires extended memory. That's a fundamental limitation. Running HP-41 machine code requires HP-41 hardware, or something that emulates HP-41 hardware accurately, and that is not something Free42 was designed to do.