Computer Clock - Clock Tick (Clock Cycle)

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1 - About

CPU's are marching forward at some frequency, and the period of this frequency is called a Clock Tick or Clock Cycle

A 100Mhz processor will receive 100,000,000 clock ticks every second.

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3 - Management

3.1 - Creation

The tick is managed/created by the clock generator

3.2 - Stop

Processor clocks may stop ticking under circumstances like the following:

  • The processor is halted when there is nothing for the CPU to do. For example, the processor may halt to save power while the computer is servicing an I/O request. When Intel Hyper-Threading Technology is enabled, both logical processors must be halted for performance-monitoring counters to be powered down.
  • The processor is asleep as a result of being halted or because of a power-management scheme. There are different levels of sleep. In the some deep sleep levels, the time-stamp counter stops counting.

3.3 - Count

The count of cycles, also known as clockticks, forms the basis for measuring how long a program takes to execute. See CPU - (CPU|Processor) Time Counter

Clockticks are also used as part of efficiency ratios like cycles per instruction (CPI).

Each core on a modern CPU has a TSC (Timestamp counter) that counts the number of ticks that have transpired.

Example: 2,59 times per nanosecond.

Property: Invariant: guarantee that the frequency will not change.

3.3.1 - Process Explorer

Clock Tick in process explorer:

  • for a process

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3.3.2 - Assembly

You can read the TSC (Timestamp counter) with the rdtsc assembly instruction.

4 - Documentation / Reference