Central Processing Unit

Lecture #4:

System Unit Motherboard Central Processing Unit

Computer Hardware we will cover today:

Components of the system unit Motherboard Central Processing Unit Control Unit ALU System Clock Coprocessors

1 What’s happening inside the computer?

Computer Architecture

CPU

Input Output Memory

Storage

2 tower model System Unit (or chassis)

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

motherboard expansion cards ports memory hard drive floppy and CD drives

Motherboard (also called system board)

The main circuit board in the computer has on it: CPU or Microprocessor chip System clock Power supply/battery Heat Sink Ports Expansion slots Buses – allow communication between components Memory - RAM and ROM

3 Major Components of a Motherboard

16 Bit ISA Slots Microprocessor Allows expansion of computer Single integrated circuit that through modem, sound and executes the majority video cards. of the instructions 32 Bit PCI Slots to process Allows expansion cards that data. can transfer data faster than ISA slots. Battery Provides power for the system clock.

Power Connector Supplies power to the motherboard. ROM BIOS Basic Input/Output System stores permanent instructions Cache RAM that start the computer. Stores and retrieves information for the microprocessor at a faster SIMM RAM Bank rate than SIMM RAM so Single Inline Memory Module instructions can be executed faster. stores data to be used by the microprocessor.

Motherboard

4 Some 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 Unit

The 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.

5 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)

0110011101110111011001110110 11100110101110111011101

Control Unit

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

instruction cycle

6 Registers

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

storing location of instruction storing instruction while decoding storing data while its being processed storing results of calculation (accumulator)

011010101010101010011010101010101101101010110101011010101010101010101011010101 01010101010101011111101010101010101010101010101010101010101010101001

Arithmetic Logic Unit

Arithmetic (+, - , x, /)

Comparative (<, = , >)

Logical (AND, OR, NOT)

0110101010101010100110101010101011011010101101010110101010101010101010110 1010101010101010101011111101010101010101010101010101010101010101010101001

7 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)

Comparing and Upgrading Processors

Chip for Chip – replace existing processor with new one Piggyback – stack new processor on top of old Daughterboard – circuit board which plugs into the motherboard to add capabilities

8 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.

Heat Sinks

9 Binary Numbers

0110011101110111011001110110111001101011101110111010011 01010101110110111011011101101110101110110111010111011 0110111011011101011111110

0 and 1 are binary digits called bits eight bit binary numbers are bytes half 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 (see page 192)

Be sure you know how to:

1. Describe the components on the mother board 2. Know what the two parts of the CPU are and what they do 3. Explain how the CPU uses the four steps of a machine cycle to process data 4. Define a bit and describe how a series of bits represents data

10 Reading Assignment: Read 193 - 200 in Discovering Computers 2005 : Memory