Just a short note to say I have finished verification of my REXCPM board. It provides up to 2MB of battery backed up SRAM in the OPTROM socket, and it is good for providing the needed full 64KB of SRAM for CP/M operation, plus provides ample space for RAM based disks. It needs only 2 wires - one connected to the /WR signal, and one connected nicad juice.
In M100, you get /WR and RAMRST (which supplies nicad juice) on the system bus connector. In T102, you solder wires to the adjacent RAM chip to get /WR and Vb. ..Steve