White 27 vs Black 517
White starts from setup 27 (NQNRBKRB), Black from setup 517 (RNBBQKNR). In the encyclopedia since 2026-11-01: neither side starts better.
|cp| ≤ 5 at 400M · 800M · 1.6B · 4B nodes, two independent engines agree
How to play with different setups
White sets up the pieces by position No. 27, Black by position No. 517, mirrored on their own side; the pawns stand as usual.
Moves as usual: White starts; everything else follows the Chess960 rules.
The two setups
White: setup #27 N Q N R B K R B
King on the f-file, rooks on d, g, queen on the b-file; one bishop starts in a corner; the knights start away from the centre. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 27 gives White +0.27 (Morozov Balance Index, 400M nodes).
Black: setup #517 R N B B Q K N R
King on the f-file, rooks on a, h, queen on the e-file; no bishop starts in a corner; the knights start on central files. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 517 gives White +0.14 (Morozov Balance Index, 400M nodes).
Why the pair is balanced
At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation is exactly 0.00 each time, reaching search depth 53.
Admission rule: |cp| ≤ 5 at four budgets up to 4 billion nodes, no one-sided drift along the ladder, and confirmation by two independent engines — Berserk and Lc0 — each below its own median on symmetric positions. The same corridor is required at every deeper budget (8 G, 16 G) at which the pair has been evaluated.
The shallow rungs wandered between -22 and +8 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.
For comparison, in symmetric play setup 27 gives White +0.27 and setup 517 gives White +0.14: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.
White is not forced into a single path: the best first move is d4, and 2 first moves are within 10 cp of it.
Along the engine's main line (16 moves) the evaluation stayed within ±20 cp the whole way: the balance holds as the pieces come out, not only on move one.
Engine self-play agrees: 10 games, White won 0, drawn 10, Black won 0 (White scored 50.0%).
Verification ladder
Nine independent searches of the starting position, each with a larger node budget. Evaluation in centipawns from White's point of view.
| Stage | Nodes | Depth | Eval, cp | Main line |
|---|---|---|---|---|
| S0 | 100 000 | 14 | +3 | 1. c4 h5 2. d4 d6 3. g3 Nf6 4. h4 Bh3+ |
| S1 | 500 000 | 17 | +5 | 1. d4 d6 2. O-O h5 3. Nd3 h4 4. c4 Nd7 |
| S2 | 2 000 000 | 22 | -22 | 1. d4 Nc6 2. c4 d6 3. Nc2 e5 4. g3 h5 |
| S3 | 8 000 000 | 29 | +8 | 1. d4 Nc6 2. c4 e5 3. Nc2 d6 4. Bc3 h5 |
| S4 | 32 000 000 | 34 | -2 | 1. d4 Nc6 2. c4 e5 3. Nc2 d6 4. Bc3 h5 |
| S5 | 128 000 000 | 40 | -10 | 1. d4 Nc6 2. c4 e5 3. Nc2 d6 4. Bc3 Nf6 |
| S6 | 400 000 000 | 45 | 0 | 1. d4 Nc6 2. c4 e5 3. Nc2 d6 4. dxe5 Nxe5 |
| S7 | 800 000 000 | 49 | 0 | 1. d4 d6 2. c4 Nc6 3. Nc2 e5 4. dxe5 Nxe5 |
| S8 | 1 600 000 000 | 53 | 0 | 1. d4 d6 2. c4 Nc6 3. Nc2 e5 4. dxe5 Nxe5 |
Deep verification
The search ladder reaches 1.6 billion nodes; admission needs a 4-billion rung and two further engines on top of that. Beyond even that, every pair was re-checked at budgets up to ten times larger and in thousands of self-play games. This section shows what each check returned for this pair.
| Nodes | Eval, cp |
|---|---|
| 4 000 000 000 | 0 |
| 8 000 000 000 | not checked |
| 16 000 000 000 | not checked |
This pair stays within the ±5 cp corridor up to 4 000 000 000 nodes.
Independent engines, run on the same position:
- Berserk 14: +9
- Lc0 0.32.1: +11
Independent confirmations: 3 of 3. An engine counts as confirming when its reading of the pair is closer to equality than its own reading of a typical symmetric Chess960 position (+10 for Berserk, +18 for Lc0). Where only one engine confirms, the pair is balanced according to that engine alone, and this page says so.
Own weight of each setup, measured against the classical array: White +30, Black +62, difference -32. A balanced pair needs White's setup to be weaker by about the price of the first move.
Extended self-play: 10 games, 0 White wins, 10 draws, 0 Black wins, White scored 50.0%.
Best first moves
The 3 best first moves for White, searched together at 400 000 000 nodes.
| # | Eval, cp | Depth | Main line |
|---|---|---|---|
| 1 | -9 | 42 | 1. d4 d6 2. c4 Nc6 3. Bc3 e5 4. Nc2 h5 5. g3 Bh3+ |
| 2 | -4 | 41 | 1. c4 d6 2. d4 Nc6 3. Nc2 e5 4. Bc3 Nf6 5. g3 Bh3+ |
| 3 | -28 | 41 | 1. g3 e5 2. c4 d6 3. d4 exd4 4. Nc2 c5 5. e3 Bg4 |
Main-line play-out
16 moves, 5 000 000 nodes per half-move. Largest |evaluation| 20 cp, mean 6.3 cp, final 0 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | d4 | +7 | Nc6 | +9 |
| 2 | c4 | +5 | d6 | -4 |
| 3 | Bc3 | -5 | e5 | -18 |
| 4 | Nc2 | -20 | h5 | -17 |
| 5 | g3 | -15 | Bh3+ | -16 |
| 6 | Ke1 | -11 | Bf5 | -13 |
| 7 | Nd3 | -8 | Nxd4 | -13 |
| 8 | Nxd4 | -16 | exd4 | -20 |
| 9 | Bxd4 | -6 | Bf6 | -2 |
| 10 | Bxf6 | 0 | Nxf6 | 0 |
| 11 | Bxb7 | 0 | Rb8 | 0 |
| 12 | Bg2 | -4 | O-O | 0 |
| 13 | Kf1 | 0 | a5 | 0 |
| 14 | Bf3 | 0 | Bh3+ | 0 |
| 15 | Bg2 | 0 | Bf5 | 0 |
| 16 | Bf3 | 0 | Bh3+ | 0 |
| 17 | Bg2 | 0 |
Engine self-play
10 games at 500 000 nodes per move: White won 0, drawn 10, Black won 0 — White scored 50.0%. Average length 37.4 moves.
Sample game 1 (1/2-1/2)
1. d4 Nf6 2. c4 d6 3. Nd3 h5 4. g3 Bh3+ 5. Bg2 Bxg2+ 6. Rxg2 b5 7. Qc1 a5 8. f3 bxc4 9. Qxc4 e6 10. Nc2 Nc6 11. Kg1 Ne7 12. Kh1 a4 13. Rc1 g5 14. Ncb4 g4 15. Rf2 a3 16. b3 h4 17. gxh4 Nf5 18. Qc6 Qxc6 19. Nxc6 Nxh4 20. Nxd8 Rxd8 21. fxg4 Nxg4 22. Rf4 f5 23. Bxh4 Rxh4 24. Rxc7 Rxh2+ 25. Kg1 Rxe2 26. d5 Ne5 27. dxe6 Nxd3 28. Rxf5+ Ke8 29. Rg5 Re1+ 30. Kh2 Re2+ 31. Kg3 Re3+ 32. Kh4 Re4+ 33. Kg3 Re3+ 34. Kh2 Re2+ 35. Kg3
Sample game 2 (1/2-1/2)
1. d4 c6 2. c4 h5 3. Nc2 Nf6 4. g3 d6 5. Ne3 Ng4 6. Nxg4 hxg4 7. O-O Nd7 8. Bg2 e5 9. Qd3 Qe6 10. dxe5 dxe5 11. Nb3 Be7 12. Bd2 O-O 13. Rfe1 b6 14. Bc3 a5 15. c5 Nxc5 16. Nxc5 Bxc5 17. Qe4 f6 18. Qxc6 Qxc6 19. Bxc6 Ra7 20. Bd5+ Kh7 21. a3 Kg6 22. Rc1 Rd8 23. Red1 Rad7 24. Bb3 Rxd1+ 25. Rxd1 Rxd1+ 26. Bxd1 Bd4 27. Bxd4 exd4 28. Kf1 Kf5 29. Ke1 Ke5 30. Kd2 Be6 31. Kd3 Bc8 32. Kd2 Kd6 33. b4 Ke5 34. Ba4 Kd6 35. f4 gxf3 36. exf3 Kd5 37. Bb5 Be6 38. Kd3 Bf5+ 39. Kd2 Bg6 40. h4 Bh5 41. Ke2 Bf7 42. Kf2 Bg6 43. Ke2 Bf5 44. Ke1 Bc8 45. Bd3 Be6 46. Ke2
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 27 / 517 in the app's encyclopedia, then choose how to play.
- Local game — two players on one device, with a clock.
- With a mentor — a clearly labelled training bot with hints, at your level.
- Challenge a friend — an online game by link; both players get the same pair, colours swap on rematch.
Play this pair against the computer, right here Play a friend
FEN (Shredder, castling rights by rook files): rnbbqknr/pppppppp/8/8/8/8/PPPPPPPP/NQNRBKRB w DGah - 0 1
Mirror twin: White 929 vs Black 538 — a different position (castling squares are fixed), not evaluated by the search.
Current place in the live balance rating: 154.