Central processing unit

The Central Processing unit (also referred to as CPU) is the part of a computer which controls all the other parts. Designs vary widely but the CPU generally consists of the, the (ALU), s, temporary s and various other logic.

Definition
The control unit fetches from memory and decodes them to produce signals which control the other parts of the computer. These signals cause it to transfer data between memory and ALU or to activate peripherals to perform input or output.

Various types of memory, including, RAM and ROM, are sometimes considered to be part of the CPU, particularly in modern microprocessors where a single may contain one or more processors as well as any or all of the above types of memory. The CPU, and any of these components that are in separate chips, are usually all located on the same, known as the. This in turn is located in the system unit (sometimes incorrectly referred to as the "CPU").

A has several CPUs or "cores" which may share other resources such as memory and peripherals.

The term "processor" has to some extent replaced "CPU", though RAM and ROM are not logically part of the processor.

Apple series
The Apple I and Apple II were based on 8-bit MOS 6502 processors, which were sufficiently powerful at the time for low cost. Apple later switched to licensed designs from other manufacturers, such as Synertek.

Apple Lisa
The Apple Lisa used 68k processors from Motorola, which drastically improved performance through 16-bit/24-bit architecture. The Motorola CPUs were also used in early Macintosh models that transitioned to 32-bit-clean architecture used in the Macintosh Quadra series.

Power Macintosh
The Power Macintosh 6100, 7100 and 8100 debut in March 1994, becoming the first computers to use PowerPC-based RISC processors designed by the AIM alliance.

Intel-based Macs
At the 2005 Worldwide Developers Conference, Apple CEO Steve Jobs announced that Apple would transition to Intel processors.

Apple Silicon
At the 2020 Worldwide Developers Conference, Apple announced that it would transition from Intel to its own processors by 2022.