The changes are:
- More aggressive pruning in search.
- Increased value of rook vs. minor and pawns if both sides have pawns.
- Improved handling of king and queen vs. king and rook.
- Compressed the bitbase for king and pawn vs. king from 32 kB to 24 kB.
- The mate searching mode is about 30% faster.
- More opening book knowledge.
- Improved protection against false opening book hits.
- Added option for aggregate castling rights in the position editor of the microcontroller version.
Here are two games of V1.40 (microcontroller version) vs. Mephisto Berlin Pro London (68020, 24 MHz), both at 30 minutes per game. The CT800 without overclocking.
The CT800 with Black opts for Modern Defence, and the BLP goes for the f2-f4 attack. The CT800 holds its ground and undermines White's pawn centre as intended. White doesn't get around to castling, but Black's king position isn't exactly a low-energy house, either. At the end of a wild game where both sides overlook possible advantages, the BLP heads for draw by threefold repetition through perpetual check.
In the rematch, the CT800 has White and chooses the pretty rare f2-f3 side variant of the Trompovsky attack, still from the embedded opening book. White castles long, Black short. White unleashes a pawn storm. The BLP, losing ground, tries a centre pawn sacrifice to get some counterplay, but White's attack is already too strong. A queen exchange lets Black fend off mate, but not the white passed pawns, and the BLP resigns.
That were the first two test games of V1.40, and not only that the CT800 has reached its first draw against the BLP, but even a win.