Re: Offer: Tandberg TDV2324 CP/M computer from the 70s
Person
09/15/23 10:16 AM
Another thing worth noting, the mentioned X-monitor seems to only be a loadable module for the TDV-2324, whereas on the TDV-21x4 it's permanently in ROM at the lower 8K of the memory map. Quite a lot of system functionality is in this monitor, and it is my guess that software uses this for everything instead of calling the hardware directly. This would also explain the good backwards-compatibility of the TDV-2324.
Looking a little bit on the disassembly, a ton of the functions in there (including every single interrupt-handler) also have optional hooks the OS can take use of. These hooks are stored (among other monitor-variables) as pointers in a reserved 2K area of RAM. On the TDV-21x4 series this memory area is made up of dedicated RAM chips on the CPU card, so it's guaranteed to be there even if there's no other RAM-expansion cards installed.