I agree with Birt, those micrograbbers are finicky. How does the wire for RexCPM connect securely in the T102?
—b9 On Mon, Aug 29, 2022 at 5:25 PM Stephen Adolph <twospru...@gmail.com> wrote: > 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. > > >
