ryant started Colossus Chess in 1983, using his White Knight Mk 11 program,winner of the 1983 European Microcomputer Chess Championship, as a basis. It was developed on an Apple II, but was first commercially released for Commodore 64 as Colossus Chess 2.0 (CDS Micro Systems, 1984). A number of releases for 8-bit microcomputers followed. Version 3.0 was released in 1984 for the Atari 8-bit family of computers (published by English Software), followed by 4.0 in 1985 which was released on most formats of the day (published by CDS). Per other games of the time, the Acorn Electron implementation required that part of the screen memory be used as working space, causing the lower half of the screen to contain ‘garbled’ patterns.
Colossus Chess featured time-controlled play with game clocks, an opening book with 3,000 positions, and problem-solving mode that could solve normal mates, selfmates and helpmates.Pondering on opponent’s time and a three-dimensional chessboard were introduced in Colossus Chess 4.0. All releases were written in the assembly language of the appropriate CPU; the ZX Spectrum version could examine an average of 170 positions per second.
Uncommon for microcomputer chess programs of the era, Colossus had a full implementation of the rules of chess, including underpromotion, the fifty-move rule, draw by repetition, and draw by insufficient material. Colossus was also able to execute all the basic checkmates, including the difficult bishop and knight checkmate.
The program was subsequently ported to Atari ST (1988), Amiga (1989) and IBM PC (1990) under the title Colossus Chess X. The new releases featured four chess sets and enhanced graphics developed with the assistance of Gary Thomlinson and Carl Cropley. The opening book was extended to 11,000 positions, and the program had the ability to learn from past playing experiences.
I developed Colossus Chess in 1983 from my existing White Knight chess program. It used various forward pruning techniques to achieve deeper, narrower tree searches than its earlier full width cousin and had a more sophisticated evaluation function. Over the following few years it was published for a large number of 8-bit micros including the Commodore 64 (the original version 2 and later version 4), BBC Micro, Acorn Electron, Apple ][, Atari, Amstrad CPC, Amstrad PCW, Sinclair Spectrum, MSX and probably a few more too! Later it was released for the 16-bit micros Atari ST, Commodore Amiga and IBM PC (now christened version ‘X’). It became one of the largest selling chess programs of all time. In all cases it was written in the assembly language of the appropriate CPU. The graphics on the later 16-bit versions were developed with the assistance of Gary Thomlinson and Carl Cropley. No work was done on the program from 1991 until 2005. However, Guildhall Leisure released a rebadged version called Colossus Chess 2000.
Colossus took part in the 1984 World Microcomputer Chess Championship in Glasgow.
In 2004 I started work on a completely new version conforming to the UCI protocol.