->  GG>> Still have a model 100 somewhere.

->  PR> I've got one of those, with 256MB!  And a stack of IMSAI
->  PR> 8080's.

->  Imsai 8080s? I did my assembly language course on those in
->  college. Used a cross assembler from a DEC something or other.
->  Started with the toggle switches, though.

Seen them.
Wire wrapped my first computer from a 5 page article in Popular
Electronics.
The RCA Cosmac Elf based on RCA's 1802 CPU.
Ran at a blazing speed of 1 MHz but could have been clocked to
3.2 MHz or 6.4 if you sprang for the ceramic packaged CPU.

->  Never bothered to learn any more assembly than that, and the
->  extensions to the Z80. Did a fair amount of Z80 assembly, and
->  machine language, though. Long ago.

Being just 20 Y.O. when I built mine for a mere 90 dollars
I became stunned when I discovered RCA wanted over 800
dollars for the assembler.

Mine also used a bidirectional bus both driving the LED outputs
and being driven by toggle switch inputs.
That, a RUN switch, memory protect, input DPDT and some housekeeping
chips and miniscule amount of RAM was all there was to it
--- Platinum Xpress/Win/WINServer v3.0pr5