A real-time clock is a clock located within a computer. It helps monitor the current time and can run on alternate power. Technically, accurate time can be kept using other methods, but there are many benefits of using a real-time clock. The fact that a real-time clock does not require much power consumption can be considered to be one of them. These clocks can be used in other electronic devices and are made by several companies that also manufacture integrated circuits.
Real-time clocks commonly are found as integrated circuits. The clocks usually are associated with personal computers, embedded systems and servers, but they can be included in a variety of electronic devices. The only requirement is the device's need for an accurate measure of time.
To be sure, finding and keeping accurate time can be achieved without using real-time clocks. There are certain advantages to employing and referencing real-time clocks, however. These clocks can be much more accurate than other time-keeping alternatives, they allow the main system to perform important tasks, and they do not consume much power. The latter can be important to a user of an electronic device that is forced to use an alternate power source.
Those who use alternate power can rest assured that their real-time clocks will perform their functions without having to rely on a primary power source. Common alternate power sources include lithium batteries and supercapacitors. Supercapacitors have the advantage of being soldered and charged multiple times. Alternate power sources also might be able to power battery-backed random access memory (RAM).
Real-time clocks can use a crystal oscillator or power line frequency to keep accurate time. The frequency of choice usually is 32.768 kilohertz (kHz), much like quartz clocks and watches. This frequency lends itself to simple binary counter circuits and can complement the function of time-keeping.
Electronic devices can even increase their functionality by using real-time clocks. Certain electronic devices can rely on real-time clocks when comparing the times of previous functions. If the functions have taken place within a designated period of time, device functions can be reduced drastically.
Several companies make real-time clocks, and many of these clocks can be found in personal computers. Their positions have changed as technology has improved. Historically, the clocks were located on motherboards. More recently, they're often found on the southbridge chip.