Mephisto (H)

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Home * Engines * Mephisto I-III

Mephisto I [1]

a family of dedicated chess computers, produced and traded by Hegener & Glaser since 1979 with programs of Elmar Henne and Thomas Nitsche. Short after winning the World Microcomputer Chess Champion title at WMCCC 1984 in Glasgow (shared), Hegener & Glaser abandoned the collaboration with Henne and Nitsche [2], and started to work with Richard Lang in continuing the Mephisto brand name, later also with programs of other professional chess programmers like Frans Morsch, Ulf Rathsman, Ed Schröder and Johan de Koning.


The Mephisto project started with an ordinary 2 line classified column "...we are looking for a chess programmer ... " by Mr. Horváth, which was discovered by Elmar Henne, who contacted his fellow student Thomas Nitsche from Technical University of Munich, who was already a well known chess programmer. Nitsche and Henne soon founded their own company P1 GmbH to focus on computer chess. When Mr. Horváth sold the whole stuff to Hegener & Glaser, a four year collaboration started in 1980.

Mephisto I, II

The mighty Mephisto I and II chess computers with their unique Briquette design ran on the RCA 1802 8-bit CMOS processor with 6 KiB of a 8KiB ROM and one KiB of RAM, the Mephisto II, released in 1981, doubled the memory sizes. The opening book was supplied by Ossi Weiner [3]. The programs were based on Nitsche's former program Orwell - a mixture of Shannon Type A and Type B strategy. The first plies of a brute-force alpha-beta search were extended by a selective layer of plausible moves [4], no quiescence search, but SOMA like exchange evaluation [5].

Mephisto III


The new Mephisto III program was written in Compiler Description Language CDL2 for high abstraction with chess pattern terms, but only 1.5-2.0 times slower than assembly. It was further possible to compile the program for different target processors. While the default Mephisto III Briquette model as well the first modular Mephisto MM I, first released in 1983, still had an 8-bit RCA CMOS processor, now with 32 KiB ROM and 4 KiB RAM, the Mephisto III-S and Mephisto Excalibur were shipped with Motorola's 68000 16-bit processor. Mephisto III-S won the the World Microcomputer Chess Champion title at WMCCC 1984 in Glasgow (shared with three other computers) [6].

The Mephisto 3-Projekt

The programs of Henne and Nitsche were famous for their very small and selective "humanlike" search trees [7] [8] . Translated quote from Das Mephisto 3-Projekt [9] :

MEPHISTO 3 divides the decision tree into 3 sections
  • Utopian moves (good, if the opponent does not do anything): A position occurs in a depth of approximately 1-3. The beginning of a combination. Nearly every move promising somehow is selected, even if the probability of success is quite small. Humans call some of these moves sacrifices.
  • Optimistic moves (good, if the opponent has only the second-best answer): The combination reached a depth of 4-8. Only moves with a probability hit rate larger than 30% are selected. ON BEHALF are this moves, which attack heavy pieces, threaten check, etc. these moves are however no sacrifices.
  • Realistic moves (good, if the opponent selects the best countermove): The position occurs in depths greater than 8. Only clear completions are examined. I.e. the program does not attack no more on suspicion, but pursues moves with high hit rate. To bring i.e. an attacked piece into security, so that the piece is really safe and not bound or overloaded.

See also


External Links

Chess Computers



  1. Mephisto I from Kurt´s Schachcomputer Homepage by Kurt Kispert (German)
  2. Interview mit Manfred Hegener (pdf), Erwerbsquelle: 10-1985, Zeitschrift Schachcomputer (Herausgeber Florian Piel), Edition 20, S. 6-8, Gerhard Piel: Neue Programme von neuen Programmierern.(German) hosted by Hein Veldhuis
  3. Mephisto I (pdf) hosted by Hein Veldhuis (Dutch, German)
  4. Thomas Nitsche (1983). The Mephisto Concept, A "Humanlike" Thinking Chess Program. Computer Chess Digest Annual 1983
  5. Ab Dezember neuer Mikroschachcomputer für 350 Mark:: Mephisto unterm Weihnachtsbaum, October 7, 1979, Computerwoche 36/1979 (German)
  6. 4th World Microcomputer Chess Championship from the ICGA Tournament Site
  7. Thomas Nitsche (1983). The Mephisto Concept, A "Humanlike" Thinking Chess Program. Computer Chess Digest Annual 1983
  8. Menschliche Spielweise und der erste Blick from Das Mephisto 3-Projekt, - Wiki
  9. Thomas Nitsche (1984). Das Mephisto 3-Projekt, Schach-Echo 7/1984 (German)
  10. Chess TV-World Cup - German free of ads regional ARD broadcaster, Drittes with Mephisto advertisement

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