Sensor Chess, (SciSys Sensor Chess)
a dedicated chess computer manufactured by SciSys with Sensory Board and 6502 processor at 2 MHz, released in 1981. The program was Julio Kaplan's first program for SciSys, persistent in a 4 KiB ROM, using only 256 byte of RAM. The computer, expandable by modules such as the Strong Play Module, the Super Classical Modul, and the Super Hypermodern Module, was endorsed by FIDE.
How to generate moves with 256 bytes RAM or less? Clearly, generation in chunks with move lists for each ply is not possible. One idea is to use the last move generated of each ply (if any), which needs to be saved on the ply stack for unmake anyway, as state of the generator, which implies target square, source square and direction, and with the help of the board array or piece list, the possible captured piece, and the moving piece. One may consider one killer or PV-move and MVV-LVA for reasonable move ordering, to otherwise use nested loops over target pieces/squares, directions, and source squares and pieces until the next move is found or no more are available.
- Sensor Chess from Chess Computer UK by Mike Watters
- SciSys - Strong Play (Sensor Chess module) (pdf) by Hein Veldhuis
- SciSys Sensor Chess from Schachcomputer.info - Wiki (German)