HP-41CX w/ XF-Module - just curious

[Sylvain Cote]

1. The TIME ROM is built-in in the HP-41CX and available as a plug-in module for the HP-41C/CV
   -> 4K Word ROM, hardwired to page 5
2. The Extended Functions/Memory ROM+RAM is built-in in the HP-41CX and available as a plug-in module for the HP-41C/CV
   -> 4K Word ROM, hardwired to page 3 in the HP-41CX or plug-in port low page in the HP-41C/CV (page 8, 10, 12, or 14)
   -> 128 RAM registers are hardwired from 64 (0x040) to 191 (0x0BF)
3. The CX Time & CX Extended Functions ROM (4K Word ROM) is built-in in the HP-41CX and not available as a plug-in module for the HP-41C/CV
   -> 4K Word ROM, hardwired to page 5 bank 1 in the HP-41CX
   

If you plug a X-F/M module in a CX machine, it will work but it will give nothing more than what you already have and you will loose a 4K page address. (see point 2)
Also, since the internal module is in a lower page than the plug-in module the 41OS will always used the internal mcode and never the plug-in mcode.
As for the RAM, I have observed the same behaviour as the ROM, internal RAM is used instead of the external RAM, although I do not remember how the chip select works at the electronic level to make this append. (I will have to check the schematics)

Sylvain