machine cycle in computer
The activities of the control unit, are composed of thousands of individual steps, each of which takes place in a fixed interval of time. These intervals are controlled by an internal electronic clock that emits ten million regular electronic pulses every second. Clock speeds are generally measured in megahertz (MHz) or million pulses per second. In general, operations within the central processing unit (CPU) of the computer take place in terms of a fixed number of clock pulses. This number determines the machine cycle for the computer. During a machine cycle, the computer can perform one machine operation. The number of machine operations required to execute a single instruction vary from instruction to instruction.
To illustrate this process, assume that the computer executes a move instruction (moving data from one place in the computer to another) and that this move instruction requires three separate machine operations for its completion. If a machine cycle is made up of five clock pulses, then the move instruction takes place in fifteen ticks of the clock. Thus, the total time required to complete the move is fifteen times the time interval of a single clock pulse. Execution of instructions takes place under the direct supervision of the control unit.
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