Interesting thread at SlashDot reminiscing about first computers. Mine was a Quest Super Elf (more about it here). This was based on RCA’s COSMAC 1802 processor, using a hex keypad & LED display. It came standard with 256k of RAM, but I had a whopping 4K on the expansion card, which also included an S-100 adapter. I never did get the S-100 video card or TTY keyboard working, so I wasn’t able to run Tiny Basic on it.
I was very surprised to discover that MSN has a COSMAC 1802 group.
The 1802 had 16 general purpose registers with a very simple & elegant instruction set. It was very easy to write machine code by hand, since the first 4 bits represented the opcode with the other 4 bits specifying a register.