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Since the Spectrum first came out there have been many chess programs written for it. As the Spectrum has become more popular there has been a greater incentive to write the best Spectrum chess program.

The two most obvious contenders for title best Spectrum chess program are Cyrus IS Chess and Superchess 3.0 by CP Software. Cyrus IS Chess is based on a program which won the 1981 European Microcomputer Chess Championship. While Superchess 3.0 comes with a guarantee from CP Software, that it will beat any other Spectrum chess program.

Both chess programs come in a well presented package which contains a cassette and an instruction booklet.

Cyrus contains two programs: one for the 16K and one for the 48K Spectrum. Both Cyrus programs have the following features:

1. Eight playing level
2. Cursor key movement of pieces
3. Auto-demonstration mode
4. It can be used as a chessboard by two humans
5. Take-back facility
6. Replay a game
7. Set up a position
8. It solves chess problems (up to mate in three)
9. Turn round board
10. Change sides during a game

The additional features for the 48K Spectrum are:

1. Full library of chess openings
2. Change colour of board and pieces
3. Print out a record of the game
4. Save game on tape (for future continuation)
5. Force the computer to make its best move

Superchess 3.0 is for the 48K Spectrum only. Its features are:

1. Ten playing levels
2. Recommended move option
3. Change sides and level of play during game
4. Set up a position
5. Self-play option
6. Technical information (how the program works). During the game Superchess gives itself a score dependent on positional factors and material advantage or loss.
7. Library of opening moves
8. Change colour scheme
9. Solve chess problems (up to mate in four)
10. List Moves

Cyrus definitely has more features than Superchess 3.0. For example, Cyrus's take-back facility is a very useful feature which Superchess lacks. There is also a replay feature which enables the beginner and expert alike to examine the previous game, and even to begin the game at a chosen point.

In order to discover the chess ability of both programs we decided to play the two programs off against each other. We attempted to play the two chess programs off at approximately equal time limits. The results are shown in table 1.

This game was between Cyrus (white) and Superchess (black). Cyrus played on level 6 and Superchess played on level 3. The game was typical of the games which were played. Cyrus played a fine opening due to its superior opening knowledge and the game reached a middlegame with a positional advantage to Cyrus. Cyrus exploited this advantage with some fine, logical play and won a pawn. However, this led to a multitude of exchanges and an endgame was reached with Cyrus having some winning chances and almost certain drawing chances.

However, in the endgame, Superchess came into its own. Its driving, delicate play forced zugzwang (the compulsion to make a move resulting in material or positional loss) upon Cyrus. Superchess then proceeded to overwhelm the depleted Cyrus and quickly concluded the game. The moves are listed in table 2.

For those of you who are not familiar with the notation used in table 2, I will briefly explain how it works. The piece to be moved is shown by the first etter of its name except for the knight which is represented by N. There is then a dash, or an x if the move captures a piece. The square to which the piece should be moved is shown by the piece which would be on the same file at the beginning of a game and then by the number of squares forward (one to eight). The symbols are KR (kings rook), QR (queen's rook), QN, KN, Q, K, QB and KB. Kingside castling is shown by 0-0 and queenside castling by 0-0-0. Check is shown by + and ! indicates a good move. If for example two rooks could move to the same square then the correct rook is shown in brackets. The moves should be worked out by looking at the board from the point of view of the person who is moving.

Superchess was the clear winner in this contest and this supports the claim that it can beat any other Spectrum chess program. Superchess seems to improve as the game goes on. Its standard opening play and weak (compared to Cyrus) opening library convey a dubious impression. Its middlegame is sound without being spectacular but its endgame is excellent and this is where it won or drew games in which it has a material or positional disadvantage. For example, in the final game, Cyrus reached the endgame three pawns up and with a better position after a brilliant combination. However, by playing outright blunders which lost Cyrus material and decentralised its pieces it enabled Superchess to draw the game with some subtle play.

Cyrus was rather a disappointment in the game just described. Often it would play an excellent opening and middlegame and then lose a "won" endgame. Sometimes on lower levels it would play nonsensical moves in the middlegame or in the endgame. For example, it would move a rook backwards and forwards for several moves which enabled Superchess to improve its position unhindered.

Both packages have room for improvement. Superchess has fewer features than Cyrus and it also has a weak opening library compared to Cyrus. Cyrus has weak endgame play and it has a habit of making nonsensical moves.

Cyrus IS Chess is written by Intelligent Software and is priced £9.95. It can be obtained from most computer software retailers. Superchess 3.0 costs £8.95 and can be obtained from CP Software.

Table 1. Results from IS Chess v Superchess play off

1. P-K4P-QB4
2. P-KB4N-QB3
3. N-QB3P-Q3
4. B-Qn5B-Q2
5. N-B3N-B3
6. P-Q3P-QR3
7. BxNBxB
8. Q-K2P-K3
9. B-K3P-Q4
10. PxPNxP
11. NxNBxN
12. B-Q2Q-KB3
13. Q-K5BxN
14. QxQPxQ
15. PxNB-N2
16. R-N10-0
17. B-QB3K-R1
18. 0-0-0P-QR4
19. R-N4P-R5
20. R(Q)N1R-N8
21. RxB!RxR
22. BxBPR(R)N1
23. R-N5P-QN3
24. K-N1P-KR3
25. R-N4!K-R2
26. BxRRxR
27. P-QB4P-KB4
28. RxR+KxR
29. K-B2K-B3
30. K-Q2K-B2
31. K-K3P-R4
32. P-R4K-N3
33. P-Q4K-82
34. P-Q5PxP
35. PxPK-K2
36. P-N3P-R6
37. K-Q3P-N4!
38. P-N4P-B5
39. K-K3K-Q2
40. P-Q6KxP
41. K-Q4Kb3!
42. K-B3K-Q4
43. K-B2K-75
44. K-Q2P-B6+
45. K-K2P-B7
46. K-Q2P-B8(Q)
47. KxQK-B6
48. K-Q1KQ6!
49. K-B1K-85
50. K-Q2KxP
51. K-Q3K-B4
52. K-B3P-N5+
53. K-Q3P-N6
54. PxPP-R7
55. K-B2P-R8(Q)
56. K-Q3Q-Q5+
57. K-B2K-N5
58. K-N1Kxp
59. K-B1Q-Q5
60. Q-Q8mate