The 10th World Microcomputer Chess Championship was held in Lyon, France on 24th-30th November 1990. The software section was won by the latest Richard Lang Mephisto program, the successor to Mephisto Portorose, scoring 6.5/7 ahead of Echec 1.9, Gideon and The King. Mephisto (Lyon) was running on a 68030 processor at 50 MHz and also won the manufacturer’s prize on a walkover.
So with another Lang/Mephisto program winning for the nth time in succession you might be inclined to doubt the particular interest of a Lyon 68020. However the Lyon did represent a significant step up with some innovative ideas incorporated.
As with previous programs Lyon was sold in three processor versions (68000 at 12 MHz, 68020 at 12 MHz, 68030 at 36 MHz). Not only was it compatible with the normal Mephisto boards - Exclusive and Munchen - but also with the newly released Bavaria piece recognition board. The Lyon 32bit modules are not compatible with the Modular board, though the 16bit module is.
Over the Portorose the principal source of improvement came from implementation of ‘singular extension’, an idea said to come from the mainframe program Deep Thought. This development improved tactical strength by extending the analysis of forcing lines (checks, captures etc). In Computer Chess Reports Larry Kaufman described a x4 faster solving of the 30 problems of the BT test, the equivalent of +120 Elo points. For more information on the BT-2450 test, see here (link).
Other Lyon program improvements included improved tactical/sacrificial ability, more rook/pawn and pawn endings knowledge, better handling of both passed pawns and king safety. The opening book was extended from 80,000 positions (10,000 lines) to 105,000 positions (13,000 lines) and now there was the choice of a special tournament book with bad lines weeded out.
New features included some extra levels, the ability to change piece values and an easier way of programming the opening book.