Hi,

The H8 bug is present in many chess computers from Saitek (since 1997, 28 years!):

Saitek Talking Chess Academy
Saitek Cosmos
Saitek Centurion
Saitek Cougar
Saitek Challenger
Saitek Expert Travel
Saitek Explorer Pro and Pewatronic Explorer Pro.


I began to work on it end of march with Cougar on Mame.
I first found the fun bug and fixed it in the first hour (Fun bug and H8 bug are not related).

I wrote the second week a "bizarre" as comment to the line generating the bug, but I moved on.
After checked the move generator and the very complex time management (partially because very scattered code) without result,
I found the origin of the H8 bug and I coding the patch may 28 for Cougar/Centurion (same rom).
This patch is 50% more long than the patch for AT time level for the Emerald Classic Plus, so it is necessary to change ... 3 bits!

Since I have fully understood the origin of the bug, I can confidently guarantee that this patch will fix all other chess computers
with the H8 bug (after finding the right offsets), and this without even having seen their program yet.

This bug stop quickly the search when a piece in h8 (necessary condition but not sufficient), so always be suspicious when the computer
reply with a bizarre move from h8 in less than 2 seconds.
Another point confirmed : the bugged code is not used with checkmate levels.

The patch for the H8 bug and Fun bug together (only for Cougar/Centurion, as no others roms are available):
The understanding of the bug give a solution (but with wasted time) for the bug with a real chess computer (or emulation without patched rom).
if no castling is possible, you can translate the position with a vertical symetry (h8 to a8, h7 to a7..) with the same color for pieces and
color to move, without a piece of the color to play in h8 (formerly in a8).
If this is the case or castling exist, the last solution is to create the same position with color of pieces and color to move exchanged (so a white queen in
h8 become a black queen in a1).

To Saitek : Now you can make new chess computers without H8 bug ;-)


Cordialy,

mychess.