I second Mike's recommendation for the memory mapping scheme.
I am running it on my current SuperElf expander. I've got IDIOT in a 32k EEPROM,
mapped at F800-FBFF. All the rest is RAM, in an AS6C1008 RAM 128kx8
from Digikey 1450-1017-ND $2.77. It's hooked up exactly as in Mike's drawing.
This also makes possible an arrangement described by Tony Hill in Ipso Facto # 21.
This allows you to locate a Monitor anywhere in address space and optionally
jump to it after RESET, RUN. I did it on my Elf. RESET, GO runs at 0000.
RESET, MONITOR, GO runs at F800. I believe the tradition of placing monitors at 8000
began with RCA's reset,run-u/run-p scheme. They seem to have done it on most of their
COSMAC boxes. This was OK when RAM was in short supply, but now it's limiting.
I've run Basic 3 under both UT62 and UT71. The serial I/O routines are at the
same addresses. The Basic I have came with UT62, from Herb's site. I believe he also
has UT71/MicroDos. I haven't found a Basic made for MicroDos. I'm looking forward
to seeing your system work. You'll be computing like it's 1984!