Alternative HP-41CL mainframe (OS ROMs) update for beta test

[hth]

(10-01-2019 06:09 AM)Ángel Martin Wrote:  So it's important to make this known to the adventurous users, warning them of overlapping use of the same memory resources. To quote a wise person: "with power comes responsibility"

Yes, be careful and know what you are doing.

Quote:PS.- How about a fail safe mechanism to restore the standard X-Mem layout? Will this only involve the control register at 040, or will the others also be impacted? My first impression is that it should be very easy to write a small MCODE routine to restore the "standard", simply re-writing those registers with the 600-Registers configuration used by the CL.

That is a possibility. Setting the [5:3] field to 000 in register 301 should suffice. Then perhaps it could use a check to see if page 4 and beyond are actually in use, and in that case perhaps prevent it until you purge some files. Restoring it would mean putting back the links in address 301, 400, 500 and so on.

Quote:PPS.- BTW this is a great enhancement, and brings me renewed interest into the ultimate hack to the OS: extending the MAIN memory to use the 000-3FF range - a much more difficult feat since the FOCAL RTN addresses scheme (stored in registers a and b) will need to be substantially altered.

Return addresses and the non-contiguous memory in page 3 and 4 are the main issues. Another issue is that it may have subtle incompatibilities with existing instructions that fiddle with the return registers (synthetic and MCODE).