CPU consists
of 6 main components:
1. CU
Control unit
2. ALU
Arithmetic logic unit
3.
Registers
4. Cache
5. Buses
6. Clock
All the
components work together to allow processing and system control.
Control Unit
(CU)
It fetches,
decodes, and executes instructions. It issues control signals that control
hardware. It moves data around the system.
Arithmetic
Logic Unit (ALU)
The ALU has
two main functions:
1. It
performs arithmetic and logical operations (decisions). The ALU is where
calculations are done and where decisions are made.
2. It acts
as a gateway between primary memory and secondary storage. Data transferred
between them passes through the ALU.
Registers
Registers
are small amounts of high-speed memory contained within the CPU. They are used
by the processor to store small amounts of data that are needed during
processing, such as:
1. The
address of the next instruction to be executed
2. The
current instruction being decoded
3. The
results of calculations
Different
processors have different numbers of registers for different purposes, but most
have some, or all, of the following:
Program
counter Memory address register (MAR) Memory data register (MDR) Current
instruction register (CIR) Accumulator (ACC)
Cache
Cache is a
small amount of high-speed random-access memory (RAM) built directly within the
processor. It is used to temporarily hold data and instructions that the processor
is likely to reuse. This allows for faster processing as the processor does not
have to wait for the data and instructions to be fetched from the RAM.
Buses
A bus is a high-speed internal connection. Buses are used to send
control signals and data between the processor and other components.
Three types of bus are used:
Address bus - carries memory
addresses from the processor to other components such as primary memory and
input/output devices. It’s a one-way pathway that allows information to pass in
one direction only, carries information about where data is stored in
memory.
Data bus - carries the actual data between
the processor and other components.
Control bus - carries control
signals from the processor to other components. The control bus also carries
the clock's pulses.
Clock
The CPU
contains a clock which is used to coordinate all the computer's component. The
clock sends out a regular electrical pulse which synchronizes (keeps in time)
all the components.
The
frequency of the pulses is known as the clock speed. Clock speed is measured in
hertz. The higher the frequency, the more instructions can be performed in any
given moment of time.
