user9850: Tim Krabbe gives this position on his list of serious promotions to rook and bishop:
[FEN "8/8/5b2/8/K7/4N3/kp6/8 w - - 0 1"]
[White "Boniface"]
[Black "Pugh"]
[Site "Bristol"]
[Date "1995"]

1. Nd1 b1=B

And states that: "Although the position was then technically won for Black, he did not manage to win, and a draw was agreed at move 92."
Can black win the resulting 2 bishops vs knight ending, and if so can it be done within 50 moves to avoid a draw? I had Stockfish 5 grind at it for almost two hours and a depth of 83 but it couldn't find a win.

user12894: http://www.thechessworld.com/resources/nalimov-endgame-tables
Per Nalimov  Endgme Tablebases the  endgame of K+2B vs. K+N is a force win for the 2Bs in a maximum of 67 moves.

user12873: I would suggest running Tablebase on the position - the program can calculate exactly how many moves until the end, provided there are six or less pieces.
In practical play, it is one of those endgames that borders on the brink between a draw and a win.  It should be a draw with constant perfect play, but in practice it is much easier to win with the 2 B's than draw with in the one Knight.
I think even Karpov failed to draw this endgame in a game he had with Kasparov, and he was renowned for his incredible technique.

user825: Try Syzygy tablebase: https://syzygy-tables.info/?fen=8/8/5b2/8/K7/8/k7/1b1N4_w_-_-_0_1

Please ignore DTZ if you don't know what it is, look at DTM. It's checkmate in 139 piles with perfect play.
No, the position is drawn under the FIDE 50-move rule.

9850: <p>Tim Krabbe gives this position on his <a href="https://timkr.home.xs4all.nl/chess2/minor.htm" rel="noreferrer">list of serious promotions to rook and bishop</a>:</p>

<pre><code>[FEN "8/8/5b2/8/K7/4N3/kp6/8 w - - 0 1"]
[White "Boniface"]
[Black "Pugh"]
[Site "Bristol"]
[Date "1995"]

1. Nd1 b1=B
</code></pre>

<p>And states that: "Although the position was then technically won for Black, he did not manage to win, and a draw was agreed at move 92."</p>

<p>Can black win the resulting 2 bishops vs knight ending, and if so can it be done within 50 moves to avoid a draw? I had Stockfish 5 grind at it for almost two hours and a depth of 83 but it couldn't find a win.</p>
 12894: <p><a href="http://www.thechessworld.com/resources/nalimov-endgame-tables" rel="nofollow noreferrer">http://www.thechessworld.com/resources/nalimov-endgame-tables</a></p>

<p>Per Nalimov  Endgme Tablebases the  endgame of K+2B vs. K+N is a force win for the 2Bs in a maximum of 67 moves.</p>
 12873: <p>I would suggest running Tablebase on the position - the program can calculate exactly how many moves until the end, provided there are six or less pieces.</p>

<p>In practical play, it is one of those endgames that borders on the brink between a draw and a win.  It should be a draw with <strong>constant</strong> perfect play, but in practice it is much easier to win with the 2 B's than draw with in the one Knight.</p>

<p>I think even Karpov failed to draw this endgame in a game he had with Kasparov, and he was renowned for his incredible technique.</p>
 825: <p>Try Syzygy tablebase: <a href="https://syzygy-tables.info/?fen=8/8/5b2/8/K7/8/k7/1b1N4_w_-_-_0_1" rel="nofollow noreferrer">https://syzygy-tables.info/?fen=8/8/5b2/8/K7/8/k7/1b1N4_w_-_-_0_1</a></p>

<p><a href="https://i.stack.imgur.com/OWpkr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OWpkr.png" alt="enter image description here"></a></p>

<p>Please ignore DTZ if you don't know what it is, look at DTM. It's <strong>checkmate in 139 piles</strong> with perfect play.</p>

<p>No, the position is drawn under the FIDE 50-move rule.</p>
