White 313 vs Black 625
White starts from setup 313 (NQRBBKRN), Black from setup 625 (BRNBKQRN). In the encyclopedia since 2026-10-09: neither side starts better.
|cp| ≤ 5 at 400M · 800M · 1.6B · 4B nodes, two independent engines agree
The two setups
White: setup #313 N Q R B B K R N
King on the f-file, rooks on c, g, queen on the b-file; no 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 313 gives White +0.36 (Morozov Balance Index, 400M nodes).
Black: setup #625 B R N B K Q R N
King on the e-file, rooks on b, g, queen on the f-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 625 gives White +0.25 (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 57.
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 -3 and +16 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.
For comparison, in symmetric play setup 313 gives White +0.36 and setup 625 gives White +0.25: 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 c4; the alternatives are slightly weaker but keep the game level.
Along the engine's main line (30 moves) the evaluation stayed within ±17 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 2, drawn 8, Black won 0 (White scored 60.0%).
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 | 12 | +12 | 1. c4 f5 2. O-O b6 3. f3 e6 4. e4 Ne7 |
| S1 | 500 000 | 20 | -3 | 1. c4 f5 2. O-O b6 3. e3 e6 4. d4 g5 |
| S2 | 2 000 000 | 26 | +16 | 1. c4 f5 2. b4 b6 3. Nb3 Qf7 4. O-O O-O |
| S3 | 8 000 000 | 31 | +13 | 1. c4 f5 2. O-O Qf7 3. b4 b6 4. e3 Ng6 |
| S4 | 32 000 000 | 37 | +8 | 1. c4 f5 2. O-O Ng6 3. b4 b6 4. e3 Qf7 |
| S5 | 128 000 000 | 41 | 0 | 1. c4 f5 2. O-O b6 3. b4 Ng6 4. e3 e5 |
| S6 | 400 000 000 | 51 | 0 | 1. c4 f5 2. O-O b6 3. b4 Ng6 4. Nb3 a5 |
| S7 | 800 000 000 | 56 | 0 | 1. c4 f5 2. O-O b6 3. b4 Ng6 4. Nb3 a5 |
| S8 | 1 600 000 000 | 57 | 0 | 1. c4 f5 2. O-O b6 3. b4 Ng6 4. Nb3 e6 |
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: +8
- 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 +26, Black +85, difference -59. A balanced pair needs White's setup to be weaker by about the price of the first move.
Extended self-play: 10 games, 2 White wins, 8 draws, 0 Black wins, White scored 60.0%.
Best first moves
The 3 best first moves for White, searched together at 400 000 000 nodes.
| # | Eval, cp | Depth | Main line |
|---|---|---|---|
| 1 | +12 | 40 | 1. c4 b6 2. O-O Ng6 3. b4 f5 4. e3 Qf7 5. f4 e6 |
| 2 | -11 | 40 | 1. O-O b5 2. f3 e6 3. c4 bxc4 4. Rxc4 f5 5. Rc3 Qf7 |
| 3 | -23 | 40 | 1. f3 b6 2. c4 Ng6 3. O-O c5 4. b4 Bc7 5. bxc5 bxc5 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 17 cp, mean 4.3 cp, final 0 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | c4 | -1 | f5 | +12 |
| 2 | b4 | +9 | b6 | +15 |
| 3 | O-O | +11 | Qf7 | +4 |
| 4 | e3 | +4 | O-O | +11 |
| 5 | f4 | +16 | e6 | +11 |
| 6 | Ng3 | +17 | Ng6 | +6 |
| 7 | d3 | +3 | Nd6 | -1 |
| 8 | Qb2 | 0 | Nh4 | +4 |
| 9 | Rf2 | +15 | Be7 | +13 |
| 10 | Bc3 | +7 | Ne8 | +10 |
| 11 | Nb3 | 0 | c5 | 0 |
| 12 | bxc5 | 0 | bxc5 | +10 |
| 13 | Bh5 | +10 | Ng6 | +8 |
| 14 | Qd2 | +8 | Nf6 | +4 |
| 15 | Bf3 | +7 | Bxf3 | +13 |
| 16 | Rxf3 | +8 | d6 | +3 |
| 17 | Rff1 | +6 | Nd7 | 0 |
| 18 | d4 | 0 | Rbc8 | -2 |
| 19 | dxc5 | -3 | Nxc5 | 0 |
| 20 | Qe2 | -1 | Rfe8 | -3 |
| 21 | Bd4 | 0 | h6 | 0 |
| 22 | Nh5 | 0 | Bf8 | 0 |
| 23 | Nxc5 | 0 | dxc5 | 0 |
| 24 | Ba1 | 0 | Rcd8 | 0 |
| 25 | h3 | 0 | e5 | 0 |
| 26 | fxe5 | 0 | Nxe5 | 0 |
| 27 | g4 | 0 | g6 | 0 |
| 28 | Nf4 | 0 | Bg7 | 0 |
| 29 | gxf5 | 0 | Qxf5 | 0 |
| 30 | Qg2 | 0 | Rd7 | 0 |
Engine self-play
10 games at 500 000 nodes per move: White won 2, drawn 8, Black won 0 — White scored 60.0%. Average length 55.0 moves.
Sample game 1 (1/2-1/2)
1. c4 b6 2. O-O Ng6 3. f4 f5 4. e3 e6 5. Bf3 Bxf3 6. Rxf3 c5 7. Rd1 Qf7 8. d4 O-O 9. Nb3 b5 10. cxb5 c4 11. Nd2 d5 12. b3 Nd6 13. bxc4 dxc4 14. Qc2 Qd7 15. a4 a6 16. bxa6 Ba5 17. Nb1 Bxe1 18. Rxe1 Ne7 19. Nc3 Nd5 20. Nf2 Nxc3 21. Qxc3 Ra8 22. Qa5 Qc6 23. Rg3 Rxa6 24. Qe5 Rf7 25. h4 c3 26. Rc1 Qxa4 27. d5 exd5 28. Rxc3 Nc4 29. Rxg7+ Rxg7 30. Qxd5+ Kh8 31. Qd8+ Rg8 32. Qd4+ Rg7 33. Qd8+ Rg8 34. Qd4+ Rg7
Sample game 2 (1/2-1/2)
1. c4 e6 2. O-O b6 3. d4 f5 4. b4 Qf7 5. e3 O-O 6. f3 Ng6 7. Nf2 Bf6 8. Nb3 Nce7 9. b5 Nh4 10. Nd3 g5 11. Ne5 Qe8 12. Qb2 d6 13. Nd3 Qf7 14. Bc3 g4 15. Nd2 Bg5 16. Nf4 h5 17. g3 Nhg6 18. Bb3 Rbe8 19. Rce1 Nxf4 20. exf4 Bf6 21. d5 exd5 22. cxd5 Bxc3 23. Qxc3 Bxd5 24. Qxc7 Bxb3 25. Nxb3 Nd5 26. Qc6 gxf3 27. Nd4 Rxe1 28. Rxe1 Nxf4 29. Nxf3 Ng6 30. Qxd6 Re8 31. Rxe8+ Qxe8 32. Qd5+ Qf7 33. Qxf7+ Kxf7 34. Kf2 Ne7 35. Ke3 Kf6 36. Kd4 f4 37. gxf4 Kf5 38. Ne5 Kxf4 39. Nc6 Nc8 40. Kd5 Kg4
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 313 / 625 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): brnbkqrn/pppppppp/8/8/8/8/PPPPPPPP/NQRBBKRN w CGbg - 0 1
Mirror twin: White 361 vs Black 235 — a different position (castling squares are fixed), not evaluated by the search.