CLASH, a new chess program for the PDP-8

[Dream.Build.Create]

John Comeau's CHEKMO-II has been the chess program for the PDP-8 since he gave it to the DECUS library in 1974: a complete game of chess in 4K words, on a machine with no multiply and no stack. Many of you have it running on your PiDP-8/I.

I've written a second chess program for the same machine, CLASH, as an experiment: would fifty years of chess programming knowledge, learned on far faster computers, translate back to the PDP-8 at its own speed?

CLASH is PDP-8 assembly, 16K words, and loads standalone from the BIN loader. It uses iterative deepening, alpha-beta with principal variation search, quiescence search, null-move pruning, pondering and repetition awareness. Its console follows CHEKMO-II's two-letter commands (PW, BD, MV and the rest), as a nod to the program that came first.

Three ways to try it:

- On lichess, with nothing to download: challenge PDP8-CLASH, or PDP8-CHEKMO for Comeau's program. Both accept games at 5 minutes and slower, and both run as their real binaries under SIMH throttled to PDP-8/e speed.

- On a PiDP-8/I or under SIMH: the core image and a SIMH setup file. CLASH needs 16K (fields 0-3), no EAE, and starts at 200; the .ini has the rest.
  https://github.com/dream-build-create/pdp8-chess/releases/download/v1.00/CLASH.BN
  https://github.com/dream-build-create/pdp8-chess/releases/download/v1.00/CLASH.ini

- On Windows: a zip with both programs. Double-click either one for its Teletype console, or load it into Arena or Cute Chess as a UCI engine.
  https://github.com/dream-build-create/pdp8-chess/releases/download/v1.00/PDP8-Chess.zip

The README, with more about both programs, is at https://github.com/dream-build-create/pdp8-chess

I'd be very interested to hear from anyone who runs it on a PiDP-8/I or real iron.

Chris Peters

[Folke Will]

Hi Chris,

tried it on my PDP8 implementation that's running on https://pdp8.app and it's running great (works even without a PiDP console attached)! To load:

1) Load Snippet -> BIN loader

2) expand Reader & Punch on PT08 

3) load your BN tape

4) set reader ON

5) set baud rate to 2400 or so for faster loading

6) toggle 7777, Load Add, Start to let the BIN loader load the tape

7) after the Run lamp turns off, toggle 0200, Load Add, Start

Now for something actual testing..

Regards,

Folke

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[Dream.Build.Create]

Hi Folke,

That is so cool!

Can I add your instructions to the readme file?

Chris.

[Folke Will]

Thanks, sure! If the assembly listing is PAL8 or Macro-8, it should even be possible to paste the listing in the Code tab, click assemble and load the result directly.

To view this discussion visit https://groups.google.com/d/msgid/pidp-8/65259971-d261-44af-a8c2-964544fc0d33n%40googlegroups.com.

[Dream.Build.Create]

I posted the .lst and .pal file to:

https://github.com/dream-build-create/pdp8-chess/releases/tag/v1.00