Bit of a step forward in terms of REXCPM for T200. In experiments on a real T200 (not virtualT), I get the following nice result.
Question: What memory is accessed in the "address hole" from 8000-9FFF" when Option ROM is selected (BANK3)? - ideally CP/M needs a full 64k - we have ram from A000-FFFF - we have "REXCPM RAM" from 0000-7FFF (when BANK3 is active) - ... and, we know that the 2nd 8K MAIN ROM is accessed from 8000-9FFF when BANK1 is active. Turns out that the Option ROM is actually chip selected for the entire address range from 0000-7FFF AND 8000-9FFF! --> when I run a "peeker" program that switches the option ROM on, and then reads back the memory value from an address, the laptop responds with the SAME value from 0000-1FFF and 8000-9FFF. --> if the option ROM socket had the A15 signal, then it could distinguish between the addresses. Said another way, If the Option ROM socket had a 33rd signal, A15, it could support 40KB worth of ROM memory. Maybe we can use something like this as an easy way to grab A15 from an internal location? https://www.ebay.ca/itm/253076010211?hash=item3aec8174e3:g:U6cAAOSwbmdZgrNP&amdata=enc%3AAQAHAAAA8O%2BKwe9wfSB0ZCf9NL04BWAEWnVZHPJ%2BT%2BHLBzEY1gVeSf7OTaXsaxnr6JwWChHUHT7prORrrMSMiHFq%2F1%2Bjtp6bDA8e9kV2jiEeIOs3%2BGUpm7kzMlXvBrqcxGnckEHOk6ddaqGdNkxwD%2BXT3mw6PRS4fvgyEb6F%2B%2B6n1HNINZA87pEbiSn7B6AZkEVbVif2zL7S0cJbabZHXoFcWtu0WhUYfu56fE4OdjuyRx%2BafocbP2PnQ%2Fn%2Fu9tCqD9TYlXbA7n%2F75Ph6UZCTUtcgh36XdeqMgK5xDfYo9C8GnRVZRhmXRc8TM82NB%2FmMpp7aSL4fA%3D%3D%7Ctkp%3ABk9SR5DLx7_dYA Steve Therefore, the only "additional signal" needed, for REXCPM in T200, is to bring A15 to the memory area.
