PDP-11 Chess VI (Belle) By Ken Thompson (1973) ported

[Jim Ablett]

Update:

Move encoding indices were sometimes getting reversed causing illegal moves.
Fixed buffer overrun causing heap corruption.
In console mode, board display not being updated between moves.
Fixed console mode play.
Fixed opening book bugs.

Proton link:
https://drive.proton.me/urls/SYXDFSN22W#s412WevZRDVY

Smash link:
https://fromsmash.com/PDP11Chess664JA

Jim.

[Tibono]

Thank you, Jim. Much appreciated.
Eric

[gepasi]

Any chance to fix the promotion bug too?
when it promotes a pawn it sends "e2e1" on the xboard protocol instead of "e2e1q" and GUIs catch this as illegal move

[Jim Ablett]

Any chance to fix the promotion bug too?
when it promotes a pawn it sends "e2e1" on the xboard protocol instead of "e2e1q" and GUIs catch this as illegal move

Hi Pedro,

Thanks for the bug report. Fixed now.

Code: Select all

/* ------------------------------------------------------------------ */
/* winboard_send_move — NOW HANDLES PROMOTIONS CORRECTLY             */
/* ------------------------------------------------------------------ */
void winboard_send_move(int move) {
    int from = (move >> 8) & 0xFF;
    int to   =  move       & 0xFF;
    int piece = board[from];

    last_engine_move = move;
    engine_has_moved = 1;

    /* Standard move */
    printf("move %c%c%c%c",
           'a' + (from % 8), '1' + (7 - from / 8),
           'a' + (to   % 8), '1' + (7 - to   / 8));

    /* Append promotion letter if it's a pawn promotion */
    if (piece == -1 && to < 8) {           /* White pawn promotes */
        printf("q");
    }
    else if (piece == 1 && to > 55) {      /* Black pawn promotes */
        printf("q");
    }

    printf("\n");
    fflush(stdout);
}

Update:
Proton link:
https://drive.proton.me/urls/SYXDFSN22W#s412WevZRDVY

Smash link:
https://fromsmash.com/PDP6ChessJA

Jim.