What is a CPU, the Central processing unit?

Cpu Moore Law Transistor


A CPU is just a device name that indicate a device that controls a computer system.

A CPU is also known as:

The fundamental operation of most CPUs, regardless of the physical form they take, is to execute a sequence of stored instructions called a machine code program. All instructions are defined in a document called an Instruction Set Architecture (ISA). Every processor that implement this ISA, need to implement each instruction described in it.

The execution of each instruction goes through four main steps (stages) that all CPUs use in their process pipeline called the instruction cycle.

A (CPU|Processor) has several (execution|processor) cores.

The threads in a multiprocessing systems (such as multi-core systems) have to share the resources of a single core:

Cpu Moore Law Transistor

Moore Law by transistor


Device interface

A CPU can communicate with other devices through two interfaces:

Processor Architecture

The central processing unit consists of two parts:




Benchmark: SPECint

Because of these problems, various standardized tests such as wiki/SPECint have been developed to attempt to measure the real effective performance in commonly used applications.


Multi-core processors

Processing performance of computers is increased by using multi-core processors, which essentially is plugging two or more individual processors (called cores in this sense) into one integrated circuit. Ideally, a dual core processor would be nearly twice as powerful as a single core processor. In practice, however, the performance gain is far less, only about fifty percent,due to, e.g.:

  • imperfect software algorithms
  • and implementation.



What usually has the greatest negative effect on processor performance?


  • b

What usually has the greatest positive effect on IO ?

  • compression !

Operating System


See Windows - Cpu (Instruction Set Architecture and word size - 32 or 64 Bit)


See CPU - Linux

Documentation / Reference

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