Functions and types of the system clock in computers

A system clock or timer uses a quartz crystal oscillator to generate pulses. These pulses are counted as the number of cycles per second. Then the cycles are counted into Hertz. A modern computer has a million (MHz)or billion hertz per second(GHz). A 3.2GHz processor means it has 3.2 billion cycles per second.

System clock speed is one of the many factors that determine how fast a computer can process data. The clock is used to synchronize all the other components that require using time for their operation. Please note that it is not the only factor since other such as processor type, RAM, and cache memory size among others will matter.

The system clock is used to maintain date and time, used by the operating system to control process execution time, providing activities timestamps among other functions. The main types of system clocks are Real-time and software clocks.

Types of the system clock on computers

Real-time clock (Hardware clock)

The real-time clock (RTC) is the main clock that is used to give the time of the day for the system. It is powered by a different power source from the main system power. 

On computers, it is powered using a CMOS battery that also powers system BIOS that ensures it is powered even when the computer is turned OFF or it is on low power mode. It is a hardware component within the computer. This system clock is located on the computer motherboard.

Software clock

This is managed by the operating system. It is used to synchronize all other operations within the computer system. It synchronizes both the software and hardware components of the computer.

Functions of the system clock in computers

  1. Maintaining the time of the day: the clock is used to give the date and time of the day. It is given in hours minutes and seconds. It is also used to operate the stopwatch if the computer supports that.
  2. Preventing processes from running longer than they are allowed to: when processes are being executed in the CPU they are timed. Clock ensures that each process doesn’t exceed the allocated time. For the time-sharing system, it ensures that each user uses the quantum of time allocated to them and no more.
  3. It is used to account for the CPU time: the clock enables the CPU to account for its time caring out respective activities. The activities can include the execution of processes or waiting for events to occur. 
  4. Handling the scheduled activities: user can schedule activities that will be triggered when a specific time is reached. Clock ensures that this is achieved. The scheduled activities include tasks like scanning for viruses, doing system backup, and system alarm among other tasks. 
  5. It gives the timestamps of activities done on the computer: when a user creates a document or a task it is given the time that it was created. Without a synchronized clock this is not possible. It also can be used on the system log to identify who logged into the system and at what time.
  6. Control the speed of BUSes and all other input-output components: different computer peripherals operate at different speeds depending on how and the type of data they consume. Clock help to synchronize between fast and slow components so that they can operate in harmony. When improving your system performance by overclocking the CPU this is the clock speed that is changed.

What is the system clock cycle?

The clock cycle measures the number of cycles that a processor executes per second. The cycle is measured in hertz. In a computer, single or multiple instructions can be executed within a single cycle depending on how the CPU is designed. In modern computers, the cycles are in billion cycles per second (GHz).

To check the system clock cycle in windows computer opens system properties or system information. You will be presented with the window below.

system information showing system clock cycle. 2.6GHz of clock cycle

This system has 2.60GHz which means it executes 2.6 Billion cycles per second.

What is epoch time?

For a system to give the time it requires to have a time reference point where it starts counting the time. Epoch time and date is an arbitrary time that the system used as its time starting point. This depends on the type of system as Wikipedia explains. 

The system record date and time by indicating the time that has elapsed from the specified epoch time of the system. The most common epoch time is the Unix epoch which starts at 00:00:00 Coordinated Universal Time (UTC) on 1 January 1970. 

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