What is a system clock in a computer?
|
An internal timing device. Using a quartz crystal, the clock in a computer breathes life into the microprocessor by feeding it a constant flow of pulses. For example, a 200 MHz CPU receives 200 million pulses per second from the clock. A 2 GHz CPU gets two billion pulses per second. Similarly, in a communications device, a clock is used to set the transmission speed and may also be used to synchronize the pulses between sender and receiver. A "real-time clock," also called the "system clock," keeps track of the time of day and makes this data available to the software. A "timesharing clock" interrupts the CPU at regular intervals and allows the operating system to divide its time between active users and/or applications. See Hertz, per clock, clockless computing and how to spoof your techie friends. The CPU Clock The quartz crystal generates continuous waves, which are converted into digital pulses. An internal timing device. Using a quartz crystal, the clock in a computer breathes life into the microprocessor by feeding it a constant flow of pulses. For example, a 200 MHz CPU receives 200 million pulses per second from the clock. A 2 GHz CPU gets two billion pulses per second. Similarly, in a communications device, a clock is used to set the transmission speed and may also be used to synchronize the pulses between sender and receiver. The quartz crystal generates continuous waves, which are converted into digital pulses. Beyond 12 Megahertz?The April 1987 issue of PC Magazine pondered the price tag of faster computers. Of course we all found out as computers reached 2 gigahertz and well beyond. (Image courtesy of PCMag.com.) Even after rebooting your computer you get exact date and time. Have you ever given it a thought that how is it possible? The answer is pretty simple; there must be an independent power source running a clock which runs even when system main power is off. Let us explore it. RTC- Real Time Clocks There are 2 clocks in a computer. One is a hardware clock known as the Real Time Clock and the other is Software Clock. Real Time Clock is battery backup power clocks so that it tracks the time even while the computer is turned off, or in low
System Clock is maintained by the kernel of an operating system and is used to set the tasks and processes – their synchronization and scheduling, settings and managing interrupts, setting timer etc. The system clock reports seconds and microseconds since a start point from the system boot up procedure. Basically the system clock is digital signal emitter, which emits signal composed of high (1) and low (0), because all the machines and their processes understand the language of binary. WorkingReal Time Clock as earlier mentioned is Integrated Circuit. It has a crystal oscillator. Crystal Oscillator uses a piezoelectric crystal to generate signals. The crystals have a crystalline structure (regular and repeated pattern of atoms). Whenever a field is applied across the crystal, its crystalline structure distorts, and on removal of the field it tends to return to its original crystalline structure, thus generating an electric signal of very precise frequency. The main property of any oscillator is frequency stability that is variation in temperature, load and change in power supply should not change the frequency of the output signal generated. Crystal oscillator excels in the field of frequency stability and is also cost effective. Generally the oscillator frequency is set to 32.768 KHz, because this is the frequency used in clocks and hence setting of system clock and timers is convenient. The powering of a Real Time Clock is done by a Lithium battery generally. RTC should also meet the requirement of minimum operational current, which has gradually drawn to as low as 100nA, so as to keep RTC running over long period of time. Whenever the motherboard is brought to power, then the battery charges automatically, hence ready for future use. Filed Under: How to |
