>> I'm building a board for the MC and the goal is 1854 uart for fast serial...
What will you be doing on the 1802 that needs/can handle 115kbps?
>> The easy way is a DIP wire wrap socket for the 1802 as then the long pins
>> can extend to a board under the MC.
That's probably the best way to deal with this. The UART, I/O group selector, etc.
can then go on the lower board. You can put off to the side a connector that mates
with the J1 on the MC switch board, and use standoffs to bolt the switch board
to the expansion board by the holes under the 25-pin connector.
>> OT if more is needed CF can be found in the 32mb to 1gb sizes.
Note that the Elf2K used a CF card. Its interface is simple and the code is available.
After studying the listing for UT71 it seems feasible to replace the lo-level disk
routines with something to run a CF card. This would eliminate the FDC system, and
allow to run ElfOs or UT71/Microdos on the same hardware. The CF card uses the same
ATA protocol that ATA/IDE hard drives do.
I am not familiar with the SD card's protocol but it seems likely that you would have
all the issues of CF or parallel EEPROM plus the bit-banger to talk i2c or SPI.
I'll read up on the SD Card interface.-good tip.