Sargon Chess Software

The notation screen from Sargon I for the Apple II

When magnetic media publishing became widely available, a US Navy petty officer, Paul Lohnes, ported Sargon to the TRS-80, altering the graphics, input, and housekeeping routines but leaving the Spracklens' chess-playing algorithm intact. Paul consulted with the Spracklens, who were both living in San Diego at the time, to make the TRS-80 version an instant success with the help of Hayden Book's newly established software division: Hayden Software. Paul was not involved in further refinements to the TRS-80 version due to his reassignment to sea duty shortly after signing the deal with Hayden Software.

In the early 1980s, SARGON CHESS was ported to the Nascom (by Bits & PCs, 1981), Exidy Sorcerer, and Sharp MZ 80K.^[7] A complete rewrite was necessary later for the Apple II, programmed by Kathleen's brother Gary Shannon. Both were published by Hayden Software.

The Spracklens made significant improvements on the original program and released Sargon II.^[1]

Sargon 2.5, sold as a ROM module for the Chafitz Modular Game System, was identical to Sargon II but incorporated pondering.^[8] It received a 1641 rating at the Paul Masson tournament in June–July 1979, and 1736 at the San Jose City College Open in January 1980.^[3]

Sargon 3.0 finished in seventh place at the October 1979 North American Computer Chess Championship. The competition had improved, but 3.0 drew against Cray Blitz and easily defeated Mychess, its main microcomputer rival. In December, 3.0 easily won the second microcomputer championship in London.^[3]

Sargon III was a complete rewrite from scratch. Instead of an exchange evaluator, this version used a capture search algorithm. Also included was a chess opening repertoire. This third version was written originally for the 6502 assembler and was commercially published by Hayden Software in 1983. Apple contacted the Spracklens and, after a port for 68000 assembly, Sargon III was the first third-party executable software for the Macintosh.^[1]

Video magazine listed Sargon III third on its list of best-selling video games in February 1985,^[9] and fourth on the best-seller list in March 1985,^[10] with II Computing listing the game second on its list of top Apple II games in October–November of the same year.^[11]

PC Magazine rated Sargon III 13.5 points out of 18. The reviewer criticized the "too abstractly drawn" pieces but praised the game's speed and skill, describing himself as "not a bad player" but only winning 10% of games at the lowest difficulty level.^[12]

After the demise of Hayden Software, later chess programs were also released under the name Sargon, including Sargon IV (Spinnaker Software), Sargon V (Activision) and a CD-i title simply named Sargon Chess. The Spracklens concurrently wrote the engines for the dedicated chess computers produced by Fidelity Electronics, which won the first four World Microcomputer Chess Championships.

The three-time world chess champion Mikhail Botvinnik played a game with Sargon in 1983 at Hamburg. He did not play his best moves but only tested the program's capabilities. Botvinnik himself was also involved in chess program development.