Bride of Son of Cheap Video: The KimKlone
laughtonelectronics.com
laughtonelectronics.com
[1]https://news.ycombinator.com/item?id=3070169
The poster, 0x12, had this to summary to offer:
"Guy expands 6502 to 16M address space by intercepting the databus and re-mapping unused opcodes and clever use of the spurious signals generated by the cpu when executing other undefined opcodes, adds a few registers to make the whole thing transparent from an assembler programmers point of view. In other words, there is no difference to the programmer between native and newly minted instructions.
On top of that he boosts the speed of his forth interpreter by concentrating on a frequently used construct called 'NEXT' in a way that should make anybody that has tried to optimize the inner loop of some VM or language proud. After all, what better way to optimize in such a situation than to be able to mold the instruction set to your desire.
He then uses this home-brew Frankenstein contraption as his benchtop computer for multiple years to do real work (instead of just shooting some pretty pictures and calling it a day)."
A block diagram and one-page description are here: http://laughtonelectronics.com/Arcana/KimKlone/Kimklone_shor...