Great pictures as usual, and some good information on the circuit too. Thanks! Some small corrections on the text, though:

The 6532 is called the RIOT: RAM, I/O and Timer. The 6530 is called the RRIOT: the extra R is for the mask ROM that was included in the 6530.

The “24″ is the mask number used by MOS (Commodore) to make the ROM, and the numbering is not limited to the CHESSmate. So there weren’t 24 versions of the CHESSmate, just 24 versions of the 6530. No-one seems to know what happened to 6530-01 but the KIM-1 had 6530-02 and 6530-03; the “TIM” RRIOT that was sold to hobbyists and contained a monitor program to debug a 6502 machine and was numbered 6530-04. There are lists (and dumps and dissassembler listings) of known RRIOT mask numbers online but I couldn’t find them quickly.

The Atari 2600 was based on the Jolt computer; it has a 6532 RIOT, not a 6530 RRIOT: all the ROM is contained in the cartridges. Without a cartridge, the VCS2600 is not even a complete computer :-)

As far as I know, the KIM-1 only ever had the two RRIOTs (02 and 03) and they are exchangeable between different revisions of the PCB (A-F?), and they are also interchangeable on the board: thanks to the programmable chip-selects it was possible for PCB designers to wire multiple sockets in parallel and let the RRIOTs decide when they would be selected. Commodore did this with the KIM-1 RRIOT’s too: one uses an active-low CE and the other uses an active-high CE.

The 6532 is not pin-compatible with the 6530 but Ruud Baltissen figured out that by inverting one address line, it was possible to emulate the KIM-1 RRIOTs using two 6532 RIOTs and one or two ROM chips (Google for “Build your own KIM-1″). Vince Briel did this to create the MicroKim. It would probably not be very hard to modify a MicroKim into a CHESSmate if you have an EPROM burner and an image file of the CHESSmate ROMs.

http://www.ebay.co.uk/itm/commodore-chessmate-boxed-/251421915721?pt=UK_VintageComputing_RL&hash=item3a89e9fa49

Chessmate up for grabs