I sent Monte an email about this, but I wanted to find out if someone else could reproduce the problem.
I wanted to play around with some physical modules and felt that the best thing to do during my exploration was address the CL Extra Functions into Page 6 (the printer page).
When I did this, I got strange behavior with the Catalogs. Catalog 1 would seem to execute OK (only the .END. was displayed with empty user program memory), but the IMDB? Function was also obviously executed as well. With YFNZ in the Alpha register, Catalog 1 returns YFNZ-0-007 in the alpha register. With an empty Alpha register, Catalog 1 returns “BAD ID”. Catalog 2 just barely starts displaying the Time function header, and then immediately aborts. However, 41CL Extra Functions can be executed from the keyboard. Catalog 3 appears to do nothing, it just returns without displaying the Catalog. Catalog 4 appears to work, except that the 41CL is unresponsive to any key presses for a few seconds after it concludes. Catalog 6 does not seem to work either. If I try to assign a function to key, as soon as I press the Alpha key to enter the function name, I get “MEMORY LOST”.
I don’t think this is expected behavior for the HP-41C when a ROM is mapped to page 6. I’m pretty sure the HEPAX module would put itself there if possible without ill effect. I am testing using – YFNS 4B at 007000, but the behavior is the same using YFNS – 4C (latest patched version) at 808000 (in RAM). It is as if the operating system is making calls directly to page 6 addresses for printer calls, but that would make Page 6 unusable for anything except a Printer ROM.
Test procedure:
Master Clear
MMUCLR
YNFZ (into alpha register)
PLUGP
MMUEN
Then try out the previous examples. I have nothing plugged into the 41CL besides the HP-41 Timer Module, in Port 2.