XOR on the ST6.
The ST6 microcontroller is small and cheap, but it has a very limited CPU.
In particular, it is missing my favorite instruction. Here's how to fix
it.
The 3op Processor is an experiment in instruction
set design. It hasn't been implemented yet.
The 65020 is a 32 bit extension of the 6502. It
also hasn't been implemented (and probably never will be).