White 503 vs Black 498
White starts from setup 503 (RQBNKNRB), Black from setup 498 (BRQNKBNR). In the encyclopedia since 2026-10-03: 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. 503, Black by position No. 498, 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 #503 R Q B N K N R B
King on the e-file, rooks on a, g, queen on the b-file; one 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 503 gives White +0.35 (Morozov Balance Index, 400M nodes).
Black: setup #498 B R Q N K B N R
King on the e-file, rooks on b, h, queen on the c-file; one 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 498 gives White +0.13 (Morozov Balance Index, 400M nodes).
Why the pair is balanced
At the deepest rungs (400M, 800M, 1.6B, 3.2B nodes) the evaluation never left ±1 centipawns of equality, reaching search depth 56.
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 ±12 cp.
For comparison, in symmetric play setup 503 gives White +0.35 and setup 498 gives White +0.13: 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 g4, and 2 first moves are within 10 cp of it.
Along the engine's main line (30 moves) the evaluation stayed within ±23 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 | 15 | +12 | 1. g4 e6 2. c4 h5 3. g5 Ne7 4. b3 b6 |
| S1 | 500 000 | 19 | 0 | 1. g4 h5 2. g5 e6 3. c4 Ne7 4. b4 b6 |
| S2 | 2 000 000 | 25 | -8 | 1. g4 h5 2. g5 e6 3. b3 Ne7 4. f4 b6 |
| S3 | 8 000 000 | 30 | -2 | 1. g4 h5 2. g5 e6 3. b3 Ne7 4. Bb2 b6 |
| S4 | 32 000 000 | 34 | +3 | 1. g4 h5 2. g5 e6 3. b3 b6 4. Bxa8 Rxa8 |
| S5 | 128 000 000 | 43 | 0 | 1. g3 e6 2. d4 b5 3. Bxa8 Rxa8 4. c3 c5 |
| S6 | 400 000 000 | 46 | +1 | 1. g3 c5 2. c3 b6 3. Bxa8 Rxa8 4. e4 e6 |
| S7 | 800 000 000 | 52 | 0 | 1. g3 c5 2. b3 e6 3. Bb2 b6 4. Bxa8 Rxa8 |
| S8 | 1 600 000 000 | 54 | 0 | 1. g3 c5 2. b3 e6 3. Bb2 b6 4. Bxa8 Rxa8 |
| S9 | 3 200 000 000 | 56 | 0 | 1. g3 c5 2. b3 e6 3. Bb2 b6 4. Bxa8 Rxa8 |
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 | -1 |
| 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: 0
- Lc0 0.32.1: +16
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 +31, Black +66, difference -35. 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 | 0 | 41 | 1. g4 b5 2. Bxa8 Rxa8 3. b4 h5 4. g5 e6 5. a4 a6 |
| 2 | -8 | 41 | 1. g3 c5 2. c3 b6 3. Bxa8 Rxa8 4. e4 e6 5. d3 d5 |
| 3 | -25 | 41 | 1. c3 b5 2. d4 e6 3. e4 d5 4. g3 dxe4 5. Bxe4 Nc6 |
Main-line play-out
30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 23 cp, mean 5.6 cp, final +11 cp.
| # | White | cp | Black | cp |
|---|---|---|---|---|
| 1 | g4 | +1 | h5 | -20 |
| 2 | g5 | -9 | e6 | -22 |
| 3 | b4 | -18 | Ne7 | -23 |
| 4 | c4 | -23 | c5 | -19 |
| 5 | Bb2 | 0 | cxb4 | 0 |
| 6 | Be5 | 0 | Ndc6 | 0 |
| 7 | Bxb8 | -7 | Qxb8 | -8 |
| 8 | e3 | 0 | b5 | 0 |
| 9 | cxb5 | 0 | Qxb5 | 0 |
| 10 | Ng3 | 0 | Qb6 | -5 |
| 11 | f4 | 0 | d5 | 0 |
| 12 | Qb2 | 0 | a5 | 0 |
| 13 | Nc3 | -2 | Ng6 | +2 |
| 14 | Na4 | 0 | Qb5 | 0 |
| 15 | Qc2 | 0 | h4 | +2 |
| 16 | Ne2 | +6 | Bd6 | +4 |
| 17 | Rc1 | +12 | O-O | +12 |
| 18 | Nc5 | +7 | Rb8 | +10 |
| 19 | Bf3 | +11 | a4 | +11 |
| 20 | Nxa4 | +11 | b3 | 0 |
| 21 | Qxb3 | 0 | Qa5 | 0 |
| 22 | Qd1 | 0 | Ba3 | 0 |
| 23 | Rc3 | +6 | Bb4 | +10 |
| 24 | O-O | +7 | Bxc3 | +7 |
| 25 | Naxc3 | +1 | Rb2 | +10 |
| 26 | d4 | +15 | Nge7 | +8 |
| 27 | Qc1 | +3 | Rb8 | +2 |
| 28 | Qd2 | +7 | Rc8 | 0 |
| 29 | Rb1 | 0 | Nf5 | 0 |
| 30 | Bg4 | +3 | Nce7 | +11 |
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 36.5 moves.
Sample game 1 (1/2-1/2)
1. g3 e6 2. d3 d5 3. a4 b6 4. Nd2 f5 5. b4 Nf6 6. f4 c5 7. b5 Nf7 8. Qb3 h5 9. Bb2 h4 10. Bf3 Bd6 11. a5 hxg3 12. hxg3 Bc7 13. Bxf6 gxf6 14. axb6 Bxb6 15. c4 Nd6 16. Nb2 Qc7 17. Kd1 O-O-O 18. Qc3 Kb8 19. Re1 Rdf8 20. Na4 Bb7 21. Nxb6 axb6 22. Kc2 Rhg8 23. Rg1 Qe7 24. Ra4 Rd8 25. Qa3 Kc7 26. Nb3 Ra8 27. Nxc5 bxc5 28. Qxc5+ Kb8 29. Rxa8+ Kxa8 30. Ra1+ Kb8 31. Qa7+ Kc8 32. Qa5 Qd7 33. b6 Kd8 34. Qb4 Ke7 35. c5 Qc6 36. Kb2 Kf7 37. d4 Nc8 38. Rh1 Rxg3 39. Rh7+ Rg7 40. Rh8 Rg8 41. Rh7+ Rg7 42. Rh8 Rg8 43. Rh7+
Sample game 2 (1/2-1/2)
1. g4 b6 2. Bxa8 Rxa8 3. c4 e6 4. Nc3 Ne7 5. d4 d5 6. Qd3 Qd7 7. Bg5 dxc4 8. Qxc4 Nd5 9. O-O-O Nxc3 10. Qxc3 Qd5 11. Bxd8 Rxd8 12. Ne3 Qb5 13. Kb1 Bd6 14. h4 O-O 15. Qc2 Bf4 16. Qc4 Qa5 17. Qb3 c6 18. a3 Qa6 19. Qc2 Bxe3 20. fxe3 Qc8 21. Qc4 b5 22. Qc5 Qc7 23. h5 Rd5 24. Qc2 b4 25. e4 Rb5 26. a4 b3 27. Qc4 Rb6 28. g5 Qf4 29. Qd3 Rb4 30. g6 fxg6 31. hxg6 h6 32. Rc1 Rxa4 33. e3 Qd6 34. Qxb3 Rb4 35. Qc3 Rb6 36. Rg2 Qe7 37. Qc5 Qh4 38. Qe5 Qe7 39. Qc5 Qf6 40. Qc4 Qf3
Play it in the CH960 app
Open this page on a phone with the CH960 app installed, or find pair 503 / 498 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): brqnkbnr/pppppppp/8/8/8/8/PPPPPPPP/RQBNKNRB w AGbh - 0 1
Mirror twin: White 546 vs Black 551 — a different position (castling squares are fixed), not evaluated by the search.
Current place in the live balance rating: 70.