CPU Clock
CPUs have electronic clocks in them, in fact it’s a fundamental part of how they operate as the electronics within a CPU have to operate in a synchronised way.
The clock is a crystal that oscillates a predictable number of times each second when electricity is passed through it. Counting these oscillations allows the computer to measure the passing of time.
- these atomic clocks use the vibrations of atoms to keep time.
Clocks are not perfectly accurate: it drifts (ie. runs faster or slower than it should). As a result, one machine may be faster or slower than another machine.
- This adds an interesting wrinkle to distributed systems, and is a reason we can't depend on the clock to determine the ordering of events.
- It is possible to synchronize clocks to some degree: the most commonly used mechanism is the Network Time Protocol (NTP), which allows the computer clock to be adjusted according to the time reported by a group of servers. The servers in turn get their time from a more accurate time source, such as a GPS receiver.
- Clock drift varies depending on the temperature of the machine.
Why use them?
The accuracy of an atomic clock matters in computing because time synchronization is critical for many computing tasks, such as
- coordinating distributed systems,
- Without accurate timekeeping, distributed systems may not be able to coordinate their activities effectively, leading to issues such as data corruption, incorrect results, or system crashes.
- scheduling tasks,
- maintaining data consistency.
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