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Release V1.33

V1.33 was released on 2019-Jan-08. You can download the release ZIP file (5 MB):

Changes from V1.32

  • Improved move sorting for quiet moves with regard to depth killers.
  • Improved move sorting resulting from internal iterative deepening.
  • When a best move is retrieved from the hash table, the move generation is deferred until the hash move has been tried without cut-off.
  • Quiescence detects stalemate against lone king.
  • Improved pawn evaluation: more penalty for isolated double pawns.
  • Improved king handling in endgames like KRPP:KR.
  • Added draw with KNP:K for rim pawns on 7th/2nd rank with defending king in the edge.
  • Improved KBP:KP with attacker rim pawn and wrong bishop.
  • The hash tables use a compressed move format which gains 16 kB of free RAM.
  • The PV lines also use the compressed move format which saves 1 kB of stack.
  • Entering moves has auto correction for swapped move squares if that converts an illegal entry into a legal one.
  • The position editor catches double entries of the same piece type.
  • In time per move mode, going into the menu and back displays the same thinking time as before instead of rounding up.
  • Refactored and improved the driver layer. The clocking allows for possible future addition of USB, and energy consumption in standby has been reduced.
  • Starting a software update may fail when the CT800 is running idle, see the troubleshooting section in the manual.


  • The Android build chain has been updated from NDK r17b to r18b.


  • A build script using Clang is supplied for generating a macOS 64 bit binary.

Known issues

All versions

  • The PV may contain an illegal move in the rare case that a PV position allows pawn takes queen with queening, but this is not the best move. However, the root move is not affected so that no illegal move will be played.

Embedded target

  • When the supply voltage exceeds 5.4 V, the firmware erroneously displays a “low battery” warning and shuts down the device.
  • When entering a new position after undoing or redoing moves, the move list in the main screen is not cleared.

UCI versions

  • The “en passant” square given via FEN position string is discarded erroneously.

Note: issues are fixed with new releases only – there are no backports. However, if an issue is found, it will be listed for the previous releases where applicable.