The endgame databases by Ken Thompson were first published in 1991. Thanks to a special compression technique, the most important endgames fit onto 4 CD-ROMs. The endgame theory owes important new insights to these endgame databases. For example, it could be proved that the endgame of two bishops versus knight is in principle won, or that in some endgames such as two bishops versus knight or two knights versus pawn more than 50 moves are needed to win. Access to the Thompson databases takes place statically. This means that the information stored in the Thompson databases is only used in the chess engine's search process when the corresponding position appears on the board.
Owing to the conceptual advantages, current programs primarily support the Syzygy databases.