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

[Ángel Martin]

(10-01-2019 01:03 AM)hth Wrote:  The additional extended memory uses the 400-EFF range of internal RAM. I left the last page F00-FFF free for future use at the moment.

Looking at the 41CL memory map I get the impression that this the same range as you are talking about here? Do you access it the usual Nut way, or do you use the NEWT specific absolute addressing (wcmd)?

Yes, it's the same range so there's an incompatibility in the designs.

The direct access functions (YSTO, YRCL, etc.) utilize the range 400-7FF (1,024 additional registers). For this I use the standard Nut way , i.e. RAMSLCT, READATA, etc. For block backup functions (YBK-ST, YBK-MM, YBK0XM, etc.) I use the WCMD though, also in the same memory range. Finally, the FOCAL routines in the same module can also reach to the upper pages (800-FFF), also for back-up purposes only.

Besides the CL Expanded Mem ROM I also tap into the expanded memory zone in the SandMatrix, to extend the storage capacity of Matrices up to 50x50 linear systems for example. For the extensions to the Matrix functions (in the SandMatrix) I utilize the three upper blocks, so from 400 to FFF. The method I used was also the standard Nut way, since the starting point were the original matrix routines - modified to allow the expanded ranges.

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"

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.

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.