A GM Endgame Mechanism

No, I'm not done with Fischer - Keres, Zurich 1959 yet. A recent post from The Chess Mind blog -- Fischer-Keres: A resignation puzzle -- answered the question why Keres resigned. It shows an endgame mechanism worth knowing.

Zurich 1959
Keres, Paul

Fischer, Robert
(After 80...Kh7-g8)
[FEN "6k1/8/6BP/5PK1/2b5/8/8/8 w - - 0 81"]

I checked the analysis with a tablebase and discovered an inaccuracy. After 81.f6 Bb3 82.Kf4 Bc4 83.Ke5, the move 83...Kh8 (lose in 15) is better than 83...Bb3 (lose in 11), which allows 84.Bf5 (win in 11) instead of 84.Kd6 (win in 15). This would only be important if a draw by the 50-move rule happened to be imminent.