[codetrotter]

   Seperator (6 bits)

   Black King pos (6 bits)

Maybe we can even skip the separator?

Since each player has to have a king on the board. So the first piece in the list is the white king, and everything after it is white, until the second king in the list, and then that one and everything after it is black.

[thrw21]

Number of chess pieces are dynamic so you wouldn't know if white pieces are over and next piece is black king (kings don't have a type bits)

But now I think about it, instead of a separator I could simple use 4 bits to represent how many (non pawn) chess pieces there are for each player. It is at most 15 (7 initial + 8 promotion) so only 4 bits instead of 6 bit seperator shaved another 4 bits!