Back in Beebug Vol. 5 No. 9, I reviewed Martin Bryant's Colossus 4 Chess, which has clearly become the best of the chess programs for the BBC micro. This position is still in no doubt - unless you own a 512 co-processor. The IBM PC range is surprisingly low in decent chess-playing programs, probably due to the Intel 8086 processor used: the 6502 and 68000 are more widely chosen for chess software. But the one exception to this is Psion Chess by Richard Lang (a very well-known name in computer chess, being responsible for the top end Mephisto machines as well as QL Chess for the Sinclair QL) - and it runs on the 512 co-processor.

The whole IBM clone range runs at an astonishing range of speeds, from the slowest IBM PC/XT to the top-end 386 machines offering an effective speed increase of over 50 times, and the 10 MHz 80186 processor in the 512 rates about 2.5 times faster than the basic XT when running Psion Chess. Psion Chess has a chess grade of 2085 in the USA on a PC/AT, so making allowances for speed and Chess Federation changes should give a British Chess Federation grade of 167 on the 512. The improvement over Colossus' 140-ish grade is verified by my tests when a 10-game match went Psion 9.5 : Colossus 0.5.

But what of the features? In many ways Psion Chess matches Colossus' features very closely. Missing are some which I never used on Colossus: legal moves displayed; invisible pieces; screen colour changes and self-mate problem mode. Colossus was rich in timing modes however, and I particularly miss the count-down and move-control modes because Psion merely has 11 normal 'average response time' levels of play, together with a 'same-as-you', 'infinite' and 8 'Mate-in-n' levels.

But loss of all these features is to my mind completely compensated not only by the much greater program strength but also the superb graphics. The partial mode 4 three-dimensional screen of Colossus is replaced with essentially a full mode 0 view of the pieces (design as in QL Chess if you've seen it). Very good, but the really impressive thing is the way the pieces slide when moving (or even resetting the board) for complete realism in playing. Game replay just has to be seen to be believed!

A press of the f2 key gives the 2D screen together with Help, optional Analysis Window and Move history. Pressing f1 gives access to 6 more help screens, and there is a facility to print the moves or the board on a printer. Key f4 even changes language to French or German! Other extra facilities include Next Best, to force the computer to think again, and Wait, which pauses the whole program.

There is just one sad thing however. Because of the way the program accesses the IBM sound chip, playing on the 512 processor leaves the game silent, so there is no audible beep when it moves, and you must keep an eye on the board because the 3D view has no supporting text to indicate whose move it is. In slow time levels I have to resort to enabling the move-print option so that I can be alerted by the printer when Psion moves, or else you could press B, which when it's the computer's move indicates (slides!) its Best-so-far move and retracts it. When it's my move, B does nothing (but H for Hint would do the same for my pieces).

So let me heartily recommend Psion Chess to novice and expert alike. The former will revel in the graphics and the latter in the strength of the program. The program is available for around 20 mail-order, and if you ever get the chance to run the disc on a PC system with Hercules monitor, be prepared for a breathtaking graphic display.

Psion Chess is readily available through shops and dealers catering for the PC games market, and at a range of prices. For example, RSC Ltd, 75 Queens Road, Watford WD1 2QN, tel. (0923) 243301 can supply it for £21.28 inc. VAT. You may be able to find other suppliers who will charge marginally less.