SF-1226 Digital Chess Clock

The Fischer rule was invented by chess world champion Bobby Fischer in 1988. It is widely used in chess, shogi, and go, and is what the SF-1226's "Bonus" mode is based on.

How it works

In a standard countdown, your time only decreases. Under the Fischer rule, every time you make a move and press the clock, a fixed number of seconds (the bonus time) is automatically added to your remaining time.

For example, with a 10-second bonus: if you have 1 minute 00 seconds left and make a move, your time becomes 1 minute 10 seconds. The bonus is added each and every move.

Difference from sudden death

In sudden death (Mode 2), running out of time means an immediate loss. With the Fischer rule, as long as you move within the bonus time each turn, you can theoretically never run out of time. This ensures a minimum amount of thinking time even in the endgame.

Choosing the bonus time

Common settings range from 5–10 seconds for casual play to 15–30 seconds for more considered games (max 60 sec on the SF-1226). A shorter main time with a longer bonus creates a good balance — fast opening play with a calmer endgame.

When the bonus is added

On the SF-1226, the bonus is added the moment you press the move button. By the time your next turn starts, the bonus is already reflected in your remaining time.

The Delay rule gives each player a fixed "grace period" at the start of every turn. The main clock does not start counting down until that grace period has elapsed. It is popular in the United States and is used in official chess tournaments.

How it works

When your turn begins, the grace period (e.g. 10 seconds) counts down first. Your main time is untouched during this window. Only after the grace period expires does your main clock start running. When you make a move, the grace period resets for your next turn.

For example, with a 10-second grace period and 5 minutes main time: as long as you move within 10 seconds every turn, your main time never decreases at all.

Difference from the Fischer rule

The Fischer rule adds time to your clock after each move. The Delay rule does not add time — it simply gives a protected window at the start of each turn. Your total time can never increase, but you are guaranteed a minimum thinking time every move.

Recommended grace period

5–15 seconds is typical (max 60 sec on the SF-1226). Too short approaches sudden death; too long extends the game considerably.

Byoyomi (秒読み) is a time control system traditionally used in professional shogi and go tournaments in Japan. After a player's main time runs out, they can continue as long as they move within a set number of seconds each turn.

While main time remains, the clock counts down normally. Once it reaches zero, byoyomi begins. During byoyomi, the player must make every move within the set seconds (e.g. 30 seconds). This countdown resets after every move.

For example, with "30-second byoyomi," once main time is gone the player can continue indefinitely — as long as every move is made within 30 seconds. Exceeding 30 seconds on any move results in a loss.

Without periods (set periods to 0)

The simplest form of byoyomi. Once main time runs out, every move must be made within the set seconds. Exceeding it even once is an immediate loss. Commonly used in go.

With periods (set periods to 1 or more)

In professional shogi and go, a number of "periods" is set (e.g. "30 seconds × 3 periods"). This means the player is allowed to exceed 30 seconds up to 3 times total. Each time they do, one period is used up. Once all periods are gone, every subsequent move must be made within the set seconds without exception. The SF-1226 supports up to 9 periods.

Why byoyomi?

Without byoyomi, a game can end abruptly the moment main time runs out — often at a critical point. Byoyomi ensures that players can continue making considered moves under time pressure, preserving the quality of the endgame.