How does a CPU Work?

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Central Processing Unit: Brains of a computer.

Inside the CPU

Different wires

carrying electrical signals (binary) around the CPU.

A steady wire,

called the Clock, keeps the electrical signal in sync.

Modern CPUs are

measured in GHz, or several billion times per second.

This speed allows

modern CPUs to perform complicated tasks easily.

NOTE:

Giga

means billion, and hertz mean seconds.

Outside the CPU

May be manufactured

from Intel or AMD.

Underneath the CPU

Pins that allow I/O

information.

Fits on the

motherboard.

Motherboard

Allows all the

components in a computer to connect to each other.

Right on the

motherboard is the RAM.

RANDOM ACCESS MEMORY

Contains all the

data being processed by the CPU.

Contains a list of

addresses.

Each of those

addresses is a piece of data.

CPU normally

requests each piece of RAM in order.

Data can be

accessed randomly if needed or instructed to do so, but it normally

accessed in order.

E.g., When the

computer runs a program, it sends an address to RAM to begin running the

program.

RAM

address:

Consists of a series of zeroes and ones, representing on and off signal

wires respectively.

Doesn't do anything

with the addresses without the SET/ENABLE wire.

May be repeatedly

done.

Save data to RAM.

Outputs the

addresses, data and turns on the set wire.

Overwrites the data

at that address with the new data.

Data inside the RAM:

Consists of:

Instruction: Tell the CPU to do

different things.

Number: Add, compare, or

process in some way.

Address: At particular

memory addresses in RAM are an address.

Used for various

reasons:

Output a number

at a particular device, you have to know the address.

Send data to the

printer or monitor.

Letter: Output text is

stored in binary in RAM.

Each letter is

composed of binary character code.

Arbitrary

character code.

Instruction Set of the CPU

Some of the pieces

of data in RAM are instructions. Each CPU has its own set of instructions

that it understands.

LOAD:

Loads a number from RAM into the CPU.

ADD: Adds two

numbers together.

STORE: Saves a

result of the addition back at the RAM to be used later on.

COMPARE: Might be a

compare instruction after the load instruction which compares two numbers

together.

To see if which

one is larger or are the same.

Useful if used

with the JUMP IF instruction.

JUMP IF: The CPU

generally requests each piece of information in RAM one order or the

other.

Sometimes the

order wants to "jump" out of order RAM address.

To process some

other instruction in memory.

Checks if another

condition is true before it jumps.