Did Cray Blitz really have a win?

This question comes from the 1986 World Computer Chess Championship.

In the following position, with black to move, Cray Blitz said that it had run out of computer time on the host computer and therefore requested an adjudication.

In the final position is: 8/2p5/2B2k2/p4bp1/3P4/6K1/1P6/8

Black, Cray Blitz, had a pawn more, but it is almost impossible to win this position, even for a strong human, much less for a computer.

Grandmaster Hort and International Master Valvo, the arbiters for the event, proceeded to spend two hours analyzing this position and finally declared it a win for black. Cray Blitz won the next game as well and was declared World Computer Chess Champion on tie-breaks.

As I recall, the winning method found by Hort and Valvo involved bringing the king all the way around with Ke7, Kd8, Kc8, Kb8, Ka7, Kb6, Ka5 (after the pawn has moved), trading pawns and then bringing the king around behind White.

Because of the horizon effect, no computer of that era could have found such a solution.

I have never been convinced that black has a win here with best play. Can somebody run this through their computer and see what the result is?

Remember, if it turns out that this position with best play is a draw and not a win for black, then Cray Blitz did not win the 1986 World Computer Chess Championship. Cray Blitz had already lost in round two. As this was a five round Swiss, a draw here would have eliminated Cray Blitz from any contention for a top prize.

I have posted this game at http://www.anusha.com/awit-rex.htm

Although this concerns events of 13 years ago, there were 59 postings about this game on the newsgroups yesterday. Certain persons have based their reputations on the result of this game.

Sam Sloan

[Event "WCCC"]
[Site "Cologne"]
[Date "1986.06.??"]
[Round "4"]
[White "Schach 2.7"]
[Black "Cray Blitz"]
[Result "0-1" adjudicated after Cray Blitz ran out of Cray]

1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Nc3 Be7 5. Bg5 O-O 6. e3 Ne4 7. Bxe7
Qxe7 8. Nxe4 dxe4 9. Nd2 e5 10. dxe5 Qxe5 11. Qc2 Na6 12. O-O-O Bg4 13. f3
exf3 14. gxf3 Bh5 15. Bd3 f5 16. Rhe1 Rad8 17. Bf1 Qxh2 18. c5 Qe5 19. c6 Kh8
20. cxb7 Nc5 21. Nc4 Qg3 22. Qxf5 Rxd1+ 23. Rxd1 Qxf3 24. Qxf3 Bxf3 25. Rd4
Bxb7 26. Be2 g6 27. Ne5 Re8 28. Ng4 Re4 29. Kd2 h5 30. Nf6 Rxd4+ 31. exd4 Ne4+ 
32. Nxe4 Bxe4 33. Ke3 Bd5 34. Kf4 Bxa2 35. Bd3 Kg7 36. Kg5 Bf7 37. Be4 a5 
38. Bc6 Bg8 39. Be4 Bh7 40. Bd3 h4 41. Bf1 Bg8 42. Bh3 Bd5 43. Bg4 Be4 
44. Kxh4 Kf6 45. Bd7 Bf5 46. Bc6 g5+ 47. Kg3 0-1 {Adjudicated a win for Black}

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