Lesson plan
Clock drift
In engineering and computing, clock drift refers to several related phenomena where a clock does not run at exactly the same rate as a reference clock. That is, after some time the clock "drifts apart" or gradually desynchronizes from the other clock. All clocks are subject to drift, causing eventual divergence unless resynchronized. In particular, the drift of crystal-based clocks used in computers requires some synchronization mechanism for any high-speed communication. Clock drift is most commonly expressed in parts-per million (ppm), in which each unit equates to 86.4 milliseconds of drift per day. Common market watches usually range from ± 1 to ± 100 ppm. More advanced clocks may even use parts-per billion, and the most accurate atomic clocks have reached an accuracy that is expressed in parts-per sextillion. Computer clock drift can be utilized to build random number generators. These can however be exploited by timing attacks.
Article summary
In engineering and computing, clock drift refers to several related phenomena where a clock does not run at exactly the same rate as a reference clock. That is, after some time the clock "drifts apart" or gradually desynchronizes from the other clock. All clocks are subject to drift, causing eventual divergence unless resynchronized. In particular, the drift of crystal-based clocks used in computers requires some synchronization mechanism for any high-speed communication. Clock drift is most commonly expressed in parts-per million (ppm), in which each unit equates to 86.4 milliseconds of drift per day. Common market watches usually range from ± 1 to ± 100 ppm. More advanced clocks may even use parts-per billion, and the most accurate atomic clocks have reached an accuracy that is expressed in parts-per sextillion. Computer clock drift can be utilized to build random number generators. These can however be exploited by timing attacks.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.