Introduction to the Processor
September 4 (Day); August 29 (Night)

Introduction to the Processor:
o
The CPU (a.k.a. processor) is the “brain” of the computer (p. 29).
o
A CPU is an electronic device that accepts input and performs some task (a.k.a.
function) based on that input. These tasks may be arithmetic (such as adding 2 + 2)
or sending an image to the video card to be displayed on the monitor (p. 29).
o
The collection of all the functions that a CPU can perform is called the CPU’s
instruction set (p. 29).
o
Software programs and different pieces of hardware send commands to the CPU
telling it to perform a function within its instruction set (p. 29).

Relationship between CPU and RAM:
o
Software programs are stored on the hard drive. These programs must be sent from
the hard drive to the CPU, but the hard drive is far too slow and cannot get data to the
CPU fast enough (p. 29).
o
To compensate for this problem, commands and data from software do not go
directly to the CPU, but rather are stored in random access memory (a.k.a. RAM).
This RAM is very fast and can best be thought of as short term memory (p. 29).
o
Data generated by the CPU must be stored somewhere and that somewhere is RAM
(p. 30).
o

Why do we not use RAM for everything (p. 30)?

Hard drives can store 1000s more data than RAM.

RAM is volatile.

All programs do not run at once.
Moving Data from RAM to the CPU:
o
The wires that connect the different components on the motherboard are known as
traces (p. 30).
o
The Northbridge is a special chip that connects RAM and the CPU and also connects
the CPU to computer’s very fastest components (p. 30).
Relationship between RAM, Northbridge, and CPU
o
The Southbridge connects the processor to the very slowest components such as the
hard drive, interrupt controller chip, etc.
o
The frontside bus is a group of 64 traces that connects the CPU, Northbridge, and
RAM (p. 30).

The CPU uses the address bus to tell the Northbridge the location in
RAM of the data it wants next.

The data bus, in turn, carries all of the data between the CPU and RAM.

The frontside bus is also known as motherboard bus or external bus.
Parts of the Frontside Bus
Northbridge also connects to other devices.
o
Cache is an area of memory that runs at speeds much greater than typical RAM.
Programming code and data can be stored temporarily in this faster RAM to speed up
the processor.

L1 Cache:

Also known as internal cache, primary cache, Level 1 cache.

Because it is built directly on the processor chip, it runs at the
speed of the processor.

L2 Cache:

Also known as external cache, secondary cache, Level 2 cache.

The L2 cache is found in the processor housing, but not on the
processor chip itself.
The Backside Bus connects Cache and the CPU

CPU Speeds:
o
The clock chip is a crystal that oscillates at a certain frequency when electricity is
applied to it (p. 32).
o
Each tick of the clock chip is known as a cycle. One measurement of the computer’s
speed is to determine the number of cycles processed per second (p. 32).
o

Hertz – 1 cycle per second

Megahertz – 1 million cycles per second

Gigahertz – 1 billion cycles per second
A CPU runs at speeds many times the speed of the clock chip. The exact amount is
known as the multiplier (p. 33).
Multipliers for the AMD Processor

Identifying a CPU:
o
Windows System Information Tool (p. 35).
o
Right-click the My Computer icon from the Desktop, and choose the Properties tab
(p. 35).
o
Physically look at the CPU by removing the case (p. 36).
o
Reboot the CPU and watch the CPU information scroll by (p. 36).
o
Download a CPU identification software program (p. 36).