Chess clock encyclopedia topics

Analog game clocks

Analog clocks (as pictured to the right) are equipped with a "flag" (a Dutch invention) that falls to indicate the exact moment the player's time has expired. Analog clocks used mechanical buttons. Pressing the button on your side physically stopped the movement of your clock and released the hold on your opponent's. The drawbacks of the mechanical clocks included accuracy and matching of the two clocks, and matching of the indicators (flags) of time expiration. Unfortunately, additional time can't easily be added for more complex time controls, especially those which call for an increment or delay on every move, such as some forms of byoyomi. Therefore more versatile digital clocks are becoming increasingly popular. Even so, some people consider analog clocks to be nicer than the digital clocks, and a malfunctioning analog clock is a less serious event than a malfunctioning digital clock.

Early development of digital game clocks

In 1973, to address the issues with analog clocks, Bruce Cheney, a Cornell University Electrical Engineering student and chess player, created the first digital chess clock as a project for an undergraduate EE course. Typical of most inventions, it was crude compared to the products on the market 30 years later and was limited by the technology that existed at the time. For example, the display was done with red LEDs. LEDs require significant power, and as a result, the clock had to be plugged in to a wall outlet. The high cost of LEDs at the time meant that only one set of digits could be displayed, that of the player whose turn it was to move. This meant that each player's time had to be multiplexed to the display when their time was running. In 1973, LSI chips were not readily or cheaply available, so all the multiplexing and logic were done using chips that consisted of four two-input TTL NAND gates, which resulted in excessive power consumption. Being plugged into the wall is obviously a major drawback, but had one advantage: the timebase for the clock was driven off of a rectified version of 60 cycle AC current. Each player had a separate counter, and, in a parallel to the original mechanical architecture, one player's counter was disabled while the other's was running. The clock only had one mode: time ran forward. It could be reset, but not set. It did not count the number of moves. But it successfully addressed the original goals of the project (accurate and matched timing).

Recent developments of digital clocks and current usage

Digital clocks and Internet gaming have spurred a wave of experimentation with more varied and complex time controls than the traditional standards. Time control is commonly used in modern chess in many different methodologies. One particularly notable development, which has gained quite wide acceptance in chess, was proposed by former world champion Bobby Fischer, who in 1988 filed for (awarded in 1989) for a new type of digital chess clock. Fischer's digital clock gave each player a fixed period of time at the start of the game and then added a small amount after each move. In this way, the players would never be desperately short of time, but games could also be completed more quickly, doing away with the need for adjournments (in which a game is left incomplete to be finished at a later date). Although it was slow to catch on, as of 2004 a very large number of top class tournaments use Fischer's system, though usually in combination with the more traditional clocks (at lower levels, more traditional clocks are still employed as they are cheaper). Other aspects of Fischer's patent, such as a synthesized voice announcing how much time the players have, thus eliminating the need for them to keep looking at the clock, have not been adopted.

Delay clocks

There are two main types of delay clocks: (1) Bronstein (invented by David Bronstein) and (2) Fischer (invented by Bobby Fischer). With a delay clock, a small amount of time is added for each move. The reason is that with a sudden-death time limit, all moves must be completed in the specified time, or the player loses. With a small delay added at each move, the player always has at least that much time to make a move. The two types of delay clocks differ in how the delay is implemented.

Bronstein delay—when it becomes a player's turn to move, the clock waits for the delay period before starting to subtract from the player's remaining time. For example, if the delay is five seconds, the clock waits for five seconds before counting down. The time is not accumulated. If the player moves within the delay period, no time is subtracted from his remaining time.

Fischer delay—after a player has made his move, the delay is added to the player's remaining time, so it will be available for his next move. If however time runs out during his move, the game ends without the delay time being added. Time can be accumulated, so if the player moves within the delay period, his remaining time actually increases. For example, if the delay time is five seconds, and a player has four seconds left on his clock, and takes two seconds to move, then on the start of his next move he will have seven seconds. On the other hand, if he starts a move with four seconds and does not complete his move within the four seconds, he loses.