White 109 vs Black 283
White starts from setup 109 (QNRBNKBR), Black from setup 283 (NRKNBRQB). In the encyclopedia since 2026-10-15: 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. 109, Black by position No. 283, 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 #109 Q N R B N K B R
King on the f-file, rooks on c, h, queen on the a-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 109 gives White +0.10 (Morozov Balance Index, 400M nodes).
Black: setup #283 N R K N B R Q B
King on the c-file, rooks on b, f, queen on the g-file; one bishop starts in a corner; the knights start away from the centre. The king already stands on a castled square, so one of the castlings moves only the rook. In ordinary symmetric play setup 283 gives White +0.27 (Morozov Balance Index, 400M nodes).
Why the pair is balanced
At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation never left ±1 centipawns of equality, 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 agreed early: from 100 thousand to 128 million nodes the evaluation never left ±9 cp.
For comparison, in symmetric play setup 109 gives White +0.10 and setup 283 gives White +0.27: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.
The engine's first choice for White is c3; the alternatives are slightly weaker but keep the game level.
Along the engine's main line (30 moves) the largest swing was 35 cp (around move 16), ending at -10 cp — the position stays playable for both sides.
Engine self-play agrees: 10 games, White won 0, drawn 9, Black won 1 (White scored 45.0%).
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 | 11 | -5 | 1. c3 f5 2. f4 Nb6 3. Bb3 Bf7 4. Bxb6 axb6 |
| S1 | 500 000 | 18 | +2 | 1. h4 f5 2. c3 Nc6 3. d4 O-O-O 4. Nd2 g6 |
| S2 | 2 000 000 | 24 | +2 | 1. h4 f5 2. c3 g6 3. d4 d6 4. Bh2 Nc6 |
| S3 | 8 000 000 | 28 | -9 | 1. h4 f5 2. c3 Nb6 3. d4 Nc6 4. Nd2 g6 |
| S4 | 32 000 000 | 33 | -5 | 1. f3 Nc6 2. a4 f5 3. a5 g5 4. c3 b6 |
| S5 | 128 000 000 | 38 | -7 | 1. c4 Nb6 2. a4 f5 3. b4 g5 4. Qa2 Bf7 |
| S6 | 400 000 000 | 46 | -1 | 1. a4 f5 2. c3 g5 3. a5 b6 4. f3 g4 |
| S7 | 800 000 000 | 46 | 0 | 1. a4 f5 2. f3 Nb6 3. a5 Nc4 4. d3 Nd6 |
| S8 | 1 600 000 000 | 53 | 0 | 1. a4 f5 2. c3 Nb6 3. a5 Nc4 4. d3 Nd6 |
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 | +4 |
| 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: -1
- Lc0 0.32.1: 0
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 +32, Black +106, difference -74. 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, 9 draws, 1 Black wins, White scored 45.0%.
Best first moves
The 3 best first moves for White, searched together at 400 000 000 nodes.
| # | Eval, cp | Depth | Main line |
|---|---|---|---|
| 1 | +18 | 38 | 1. c3 f5 2. b4 g5 3. f3 Nb6 4. a4 g4 5. a5 Nc4 |
| 2 | +6 | 38 | 1. a4 f5 2. f3 Nb6 3. a5 Nc4 4. d3 Nd6 5. c4 g5 |
| 3 | +5 | 38 | 1. f3 Nb6 2. c3 f5 3. b4 g5 4. a4 g4 5. a5 Nc4 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 35 cp, mean 15.8 cp, final -10 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | h4 | -3 | g6 | -16 |
| 2 | c3 | -9 | f5 | -11 |
| 3 | Bh2 | -11 | Nc6 | -11 |
| 4 | e3 | -20 | O-O-O | -21 |
| 5 | a4 | -19 | h6 | 0 |
| 6 | d4 | 0 | g5 | -11 |
| 7 | Nd2 | -12 | e5 | -12 |
| 8 | O-O | -15 | f4 | -5 |
| 9 | a5 | -6 | a6 | -10 |
| 10 | b4 | -3 | Kb8 | 0 |
| 11 | h5 | -17 | exd4 | -18 |
| 12 | cxd4 | -18 | g4 | -24 |
| 13 | b5 | -16 | axb5 | -13 |
| 14 | Bxf4 | -16 | Rxf4 | -24 |
| 15 | exf4 | -24 | Bxh5 | -22 |
| 16 | Qa3 | -30 | Qf8 | -35 |
| 17 | Qxf8 | -28 | Rxf8 | -30 |
| 18 | g3 | -27 | Bxd4 | -32 |
| 19 | Rb1 | -27 | b4 | -26 |
| 20 | Nc2 | -23 | Bc3 | -25 |
| 21 | Ne4 | -20 | Bg6 | -20 |
| 22 | Nxc3 | -18 | bxc3 | -19 |
| 23 | f3 | -20 | gxf3 | -20 |
| 24 | Rc1 | -18 | Nxa5 | -18 |
| 25 | Nb4 | -20 | Nb6 | -12 |
| 26 | Rxc3 | -16 | Nac4 | -17 |
| 27 | Rf2 | -8 | Nd6 | -12 |
| 28 | Bxf3 | -16 | Be4 | -12 |
| 29 | Kg2 | -1 | c6 | -3 |
| 30 | Rc1 | 0 | Kc7 | -10 |
Engine self-play
10 games at 500 000 nodes per move: White won 0, drawn 9, Black won 1 — White scored 45.0%. Average length 48.9 moves.
Sample game 1 (1/2-1/2)
1. a4 f5 2. h4 g6 3. c3 d6 4. d4 a5 5. Bh2 Nb6 6. Nd2 Nc6 7. e3 e5 8. O-O O-O-O 9. b4 exd4 10. exd4 axb4 11. Nef3 bxc3 12. Qxc3 Qd5 13. Bb3 Qa5 14. Qc2 Bf7 15. Ng5 Bxb3 16. Nxb3 Qxa4 17. Ne6 Rf7 18. Nxd8 Kxd8 19. Qd3 Bf6 20. Rfd1 Re7 21. Bf4 Nd5 22. Bd2 Ncb4 23. Qf3 Qb5 24. Bxb4 Nxb4 25. Ra1 Qd5 26. Nc5 Ke8 27. Qxd5 Nxd5 28. Ra8+ Kf7 29. Nxb7 Nc3 30. Nd8+ Kg7 31. Rda1 Ne2+ 32. Kf1 Nxd4 33. R1a4 Kh6 34. g3 Rd7 35. Rc8 Kh5 36. Kg2 h6 37. Rxd4 Bxd4 38. Ne6 Be5 39. Nxc7 d5 40. Ne6 g5 41. Re8 Bc3 42. Nc5 Rd6 43. Nd3 Bd4 44. Kf3 Rc6 45. Nb4 Rc3+ 46. Kg2 Kg4 47. hxg5 Rf3 48. Re2 hxg5 49. Rd2 Bxf2 50. Nxd5 Bxg3 51. Nf6+ Kf4 52. Nd5+ Ke4 53. Nf6+ Ke3 54. Nd5+ Kxd2 55. Kxf3 Be5 56. Ne3
Sample game 2 (1/2-1/2)
1. h4 d6 2. c3 f5 3. f3 Nc6 4. b4 Bf7 5. b5 Na5 6. d3 c5 7. bxc6 Nxc6 8. Nd2 Nc7 9. Qb2 g6 10. e4 Bf6 11. f4 Qg7 12. Bf2 e5 13. fxe5 Nxe5 14. O-O O-O 15. Bg3 Ne6 16. d4 Nxd4 17. cxd4 Nd3 18. Qb1 Nxc1 19. Qxc1 Bxd4+ 20. Kh1 Be3 21. Bxd6 Qd4 22. Bxf8 Bxd2 23. Bc5 Qd8 24. Qb2 Bxe1 25. Bb3 Qxh4+ 26. Kg1 Bg3 27. Bxf7+ Kxf7 28. Qb3+ Kf6 29. Qc3+ Kf7 30. Qc4+ Kf6 31. Qc3+ Kf7 32. Qb3+ Kg7 33. Bd4+ Kh6 34. Rxf5 Qh2+ 35. Kf1 Qh1+ 36. Bg1 gxf5 37. Qxg3 Rf8 38. Qd6+ Kg7 39. Qe5+ Rf6 40. exf5 Kf7
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 109 / 283 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): nrknbrqb/pppppppp/8/8/8/8/PPPPPPPP/QNRBNKBR w CHbf - 0 1
Mirror twin: White 856 vs Black 577 — a different position (castling squares are fixed), not evaluated by the search.
Current place in the live balance rating: 446.