Hardware & SoftwareHardware & Software

The CPU &The CPU &MemoryMemory

The Central Processing UnitThe Central Processing Unit

The central processing unit is the mainmain chip in the computer. CPU: Central Processing UnitCPU: Central Processing Unit

– The CPU processes instructions, performs calculations and manages the flow of information through a computer system.

– The CPU performs millions of calculations every second.

Currently, Currently, CPU speed CPU speed is measured is measured in MHz or in MHz or GHzGHz

The Central Processing UnitThe Central Processing Unit

Data is Data is transported transported from from RAMRAM to the to the CPUCPU for for processingprocessing

The Central Processing UnitThe Central Processing Unit

The CPU has The CPU has two main two main parts. parts.

The The controlcontrol unit and the unit and the ALUALU

The ALUALU is the arithmetic/ logic unit.

• It performs arithmetic operations such as addition 3 - 4

• and logic comparisons such as 12 > 4

5. The results are transported back along the data bus to RAM

ALU

Control Unit

RAM

Register 1 2

Register 2 4

6

Accumulator

1. Data is transported along the data bus to the ALU registers

ADD

2. Instructions are transported to the control unit

3. The control unit indicates which operation should be carried out

4. The ALU carries out the operation and puts the results in the accumulator

Choosing a CPUChoosing a CPU

Manufacturer: Manufacturer: Most popular CPUs for Personal Computers (PC) are made by Intel.

Other CPU manufacturer’s are AMD and Cyrix.

Generation:Generation:   Each generation of CPUs is more powerful than the last.

   Newer CPUs can process more instructions at a time.

  Generations include 286, 386, 486, Pentiums, Pentium MMX, Pentium II, Pentium III and currently Pentium IV.

Speed:Speed:    Each CPU generation is available in different speeds.

  The CPU speed is a major factor in determining how fast a computer operates.

  Generally, the faster the speed, the faster the computer operates.  The speed of a CPU is measured in megahertz (MHz or GHz).

Types of CPUTypes of CPU

PentiumPentium: :

Intel’s Pentium Chip, ideal for computers using Windows 3.1 / 95 and 98.

Commons speeds: 75, 90,133, 166 and 200Mhz.

Compatible CPU chips include Cyrix 6x86 & GX as well as AMD-K5 chip

Pentium Pentium MMX:MMX:

Advancement of the Pentium chip to include Multimedia Extensions, referred to as MMX.

MMX improves multimedia tasks such as processing graphics, video & sound.

Pentium Pentium II & III:II & III:

Support MMX technology for improved multimedia performance.

Speeds from 233Mhz up to 600Mhz.

Compatible CPU chips include Cyrix 6x86MX & MII, as well as AMD-K6 chip.

Celeron:Celeron: Fast and inexpensive CPU chip, made by Intel.

Based on Pentium II chips, but with less built-in memory.

Meets the needs and budgets of most home computer users.

Current /Current /Future:Future:

The next generation of CPUs have bridged & exceeded the 1000Mhz or 1GHZ barrier. These include Intel P4 and AMD-Athlon, AMD-Duron and AMD XP

Computer MemoryComputer Memory

• Two Types of Computer MemoryTwo Types of Computer Memory

– Primary Storage (memory) • RAM and ROM

– Secondary Storage • hard drives, floppies, CD-ROMS

magnetic tape, etc

Below is a picture of 72 pin RAM. Used in PI and PII computers.

Today we currently use Dimms or DDR RAM

Primary Memory - RAMPrimary Memory - RAM

RAM is short for Random Access Memory

RAM is used to hold data temporarily before and after it is processed

Every RAM location - Every RAM location -

has an address and holds one byte of data. Remember, a byte is made up of 8 capacitors that are called bits.

A charged capacitor would represent an ON bit or 1

An uncharged capacitor would represent an OFF bit or 0

Every RAM location - Every RAM location -

has an address and holds one byte of data. Remember, a byte is made up of 8 capacitors that are called bits.

A charged capacitor would represent an ON bit or 1

An uncharged capacitor would represent an OFF bit or 0

The pattern in the The pattern in the top row represents top row represents the letter the letter AA

A different pattern A different pattern might represent a might represent a different letter or even different letter or even a number a number

Primary Memory - RAMPrimary Memory - RAM

RAM also holds Operating System instructions

RAM holds application software instructions and data

What’s so important about RAM?What’s so important about RAM?

RAM holds data ready to be sent to the processor.

RAM also holds the instructions for how to process the data.

RAM also holds operating system instructions that control the basic functions of the computer. Every time you boot up a computer, these instructions are loaded from the hard disk into RAM ready for when the processor wants them. The instructions stay in RAM till you switch off the computer.

What’s so important about RAM?What’s so important about RAM?

RAM holds data ready to be sent to the processor.

RAM also holds the instructions for how to process the data.

RAM also holds operating system instructions that control the basic functions of the computer. Every time you boot up a computer, these instructions are loaded from the hard disk into RAM ready for when the processor wants them. The instructions stay in RAM till you switch off the computer.

Primary Memory - RAMPrimary Memory - RAM

A high specification computer may have large amounts of RAM.

Currently, it is quite possible to have up to 3 gigabytes of RAM.

This is the nearly

3000 megabytes of RAM

Modern motherboards will typically have three slots for RAM. Each slot may take up to 512 Mb or more of RAM depending on the motherboard.

Older motherboards cannot hold as much RAM

Ram Capacity:Ram Capacity:

The storage capacity of RAM is measured in megabytes. Typically a PC today would have about 512 Mb or RAM

The amount of RAM your computer needs depends on the operating system you are running and what application software you have.

Windows XP requires more RAM than say Windows 98

Ram Capacity:Ram Capacity:

The storage capacity of RAM is measured in megabytes. Typically a PC today would have about 512 Mb or RAM

The amount of RAM your computer needs depends on the operating system you are running and what application software you have.

Windows XP requires more RAM than say Windows 98

Primary & Secondary StoragePrimary & Secondary Storage

Volatile means that power is required to keep hold of the data

If the power is turned off the data is lost

• DifferencesDifferences

– RAM is volatilevolatile..

– Secondary storage is non-volatilenon-volatile

Ram is volatile. This means it requires power to hold data. If the computer is turned off then all the data is lost.

A hard disk holds data even when the power to the computer is turned off

Ram is volatile. This means it requires power to hold data. If the computer is turned off then all the data is lost.

A hard disk holds data even when the power to the computer is turned off

Primary & Secondary StoragePrimary & Secondary Storage

• DifferencesDifferences

– RAM: accessing data is fasterfaster

– Secondary storage: accessing data is slowerslower

Read Only MemoryRead Only Memory

The computer BIOS is Read Only Memory (ROM)

ROM is READ ONLY MEMORY.

There is a ROM chip on the computer motherboard that holds the initial instructions so that the computer can boot up.

Let’s think about why we need ROM

The operating system is stored on the hard disk. The operating system holds the instructions for controlling the computer. When you first boot up a computer, RAM is empty. The computer has to be told how to get the operating instructions from the hard drive and place them in RAM.

ROM tells the computer how to do this.

ROM is READ ONLY MEMORY.

There is a ROM chip on the computer motherboard that holds the initial instructions so that the computer can boot up.

Let’s think about why we need ROM

The operating system is stored on the hard disk. The operating system holds the instructions for controlling the computer. When you first boot up a computer, RAM is empty. The computer has to be told how to get the operating instructions from the hard drive and place them in RAM.

ROM tells the computer how to do this.

ROM also holds instructions so that when the computer boots up it can carry out a Power On Self Test. It checks to see if a keyboard is present, if RAM is healthy and how much of it there is, how many hard drives there are and how big they are, if a floppy drive is present and working.

ROM also holds instructions so that when the computer boots up it can carry out a Power On Self Test. It checks to see if a keyboard is present, if RAM is healthy and how much of it there is, how many hard drives there are and how big they are, if a floppy drive is present and working.