Today’s lecture is all about the System Unit, the Motherboard , and the Central Processing Unit, Oh My!

Or “what’s happening inside the computer?”

Computer ArchitectureComputer Architecture

Input OutputMemory

a.k.a.

RAM

Storage

CPU

System Unit (or chassis)

The box-like case that houses the electronic components of the computer.

• motherboard• expansion cards• hard drive• floppy and CD drives• bays• power supply

tower model

MotherboardThe main circuit board in the computer

contains:• CPU or Microprocessor chip• System clock• Power supply/battery• Heat Sink• Ports• Expansion slots• Buses – allow communication between

components• Memory - RAM and ROM

Major Components of a Motherboard

RAM Single Inline Memory Module stores data to be used by the microprocessor.

BIOSBasic Input/Output Systemstores permanent instructionsthat start the computer.

Power ConnectorSupplies power to themotherboard.

16 Bit ISA SlotsAllows expansion of computer through modem, sound and video cards.

32 Bit PCI SlotsAllows expansion cards thatcan transfer data faster thanISA slots. Battery

Provides power for the system clock.

Cache RAMStores and retrieves informationfor the microprocessor at a faster rate than SIMM RAM so instructions can be executed faster.

MicroprocessorSingle integrated circuit that executes the majority of the instructionsto processdata.

Definitions

• Integrated circuit – microscopic pathway capable of carrying electric current, contain transistors, diodes, capacitors, and resistors that act as the gates (electronic switches).

• Chip – small semi-conducting material that contains integrated circuit(s) (often used interchangeably with integrated circuit).

Central Processing UnitCentral Processing UnitThe Central Processing

Unit, also called the microprocessor or chip, is the brain of the computer. It interprets and carries out the instructions that operate a computer.

The CPU has two parts:

• The Control Unit coordinates and controls all parts of the computer

• The Arithmetic Logic Unit does all the processing and calculations (including word processing)

011001110111011101100111011011100110101110111011101

Control Unit1. gets instruction from memory (called

fetching)2. translates the instruction (decoding)3. performs the command (executing)4. writes result to memory (storing)

instruction

cycle

Registers – are special high-speed storage locations in the processor that temporarily hold data and instructions during the machine cycle.

storing location of instructionstoring instruction while decodingstoring data while its being processedstoring results of calculation

(accumulator)

011010101010101010011010101010101101101010110101011010101010101010101011010101010101010101010111111010101010101010101010101010101010101010

Arithmetic Logic Unit

• Arithmetic (+, - , x, /)

• Comparative (<, = , >)

• Logical (AND, OR, NOT)

0110101010101010100110101010101011011010101101010110101010101010101010110101010101010101010101111110101010101010101010101010101011

Binary Numbers01100111011101110110011101101110011010111011

101110100110101010111011011101101110110111

0 and 1 are binary digits called bitseight bit binary numbers are byteshalf of a byte (4 bits) is a nibble

One byte represents 256 separate symbols or characters

Characters and symbols are defined using a coding scheme like ASCII

Coding Schemes

0011 0100 = 4

0011 0110 = 6

0100 0101 = E

System Clock

• generates regular pulses or ticks• each tick is a clock cycle• clock speed (or rate) is the speed at which a

processor executes instructions

• Clock speeds are measured in megahertz (one million ticks per second) and gigahertz (one billion ticks per second)

Speeding things up

• Pipelining – CPU begins executing a second instruction before the previous instruction has completed its machine cycle.

• Coprocessors – additional processor chip that assists the processor in performing specific tasks.

• Parallel Processors – Using more than one processor to divide up the work.

Parallel Processing

Heat Sinks

Be sure you know how to:• Identify the components on the motherboard• Explain what the two parts of the CPU do• Explain how the CPU uses the four steps of a machine cycle to

process data• Define the term, register• Describe the arithmetic, comparative and logical operations

performed by the ALU• Explain why programmers use binary and hexadecimal numbers• Describe how a series of bits represents data (coding schemes)• Define the terms bit, byte and nibble• Convert numbers between binary, decimal and hexadecimal

number systems• Explain the function of the system clock • Define pipelining, parallel processing and co-processors