VERY VERY interesting. I like the 2 address bits that are used only on the IIcx/IIci, that's fascinating. Interestingly, Pins 4 and 5 (A0 & A1) correspond with the A0 and A1 of the onboard ROM of my IIci, so i'm not exactly sure what this means. Also the alternate chip select (Pin 63) is interesting.

Click to expand...

Methinks the alternate chip select will likely nullify the on-board ROM. Interestingly enough, the Portable's ROM SIMM can be used ALONG WITH the on-board ROM or it can replace the on-board ROM.

The ROM SIMM Slot on the Portable, IIRC, can address 4 MB of ROM and there are instructions/hints about designing and utilizing said ROM overage in GttMFH: Second Edition.

Just imagine the possibilities: the entire operating system and a small (?) boatload of data could be burned into modern ROM ICs with faster operating speeds than the RAM ICs of the Portable's vintage!

=8-b. . . . . . .