The Fidelity Excel Mach IV Master deserves a prominent place in the story of Fidelity’s struggles to try to wrest the World Championship from Mephisto. A quest in which Fidelity failed despite Dan and Kathe Spracklen making considerable progress with the strength of their program. You can read about Mephisto’s triumph over Fidelity in my piece on the Mephisto Almeria Turniermaschine here (link). At the 1988 World Microcomputer Chess Championships Fidelity used special fan cooled cases and 68030 processors but otherwise their tournament machines were essentially Mach IV Masters.
This particular Mach IV actually played a part in Fidelity’s downfall. It was used as a test machine by Richard Lang playing games against his chess program using the connecting cable to his development computer. Otherwise the Mach IV is a standard machine. So it has a 68020 32bit processor running at 20 MHz, a 64 KB program ROM and 534 KB of RAM. 512 KB for Hash Tables. There is a 28,000 half move opening book.
The Excel Mach IV has a rating of 2075 Elo (Selective Search) and 2123 Elo (at Active Chess). Apart from the 32 bit processor running at 20MHz and the large increase in RAM for Hash Tables the Mach IV is basically the same machine as the Mach III. The manual, box (apart from stickers) and chesspieces are the same. You can see a Mach III in the photos below, which was also originally owned by Richard Lang and used for testing purposes.
I do not know how many Excel Mach IV’s were built, but they are hard to find today. When first released for sale to the public back in 1989 they cost £1299 ($2000 in the USA). £3200 at 2019 prices. A 32 bit processor and that much RAM were expensive components in 1989. So this was an expensive and rare item even without it’s connection to Richard Lang and the battle for the World Championship, which I think may make it unique.