Hardware
Processors
A bit of History
• In the 40’s the first computer (ENIAC) used
vacuum tubes to control the flow of electrons
in a vacuum. The tubes acted as switches,
which would send signals to the processor for
processing.
• The invention of the transistor changed that- it
is a tiny electronically operated switch that can
alternate between ‘on’ and ‘off’ millions of
times per second.
• Transistors are part of integrated circuitscircuits that include wires are formed together
on a single chip which is usually made of
silicon.
• Integrated circuits are known as solid-state
technology where electrons travel through
solid material rather than a vacuum.
• Chips contain millions of micro-miniature
electronic circuit components, mainly
transistors. There are different kinds of chips
eg microprocessor, memory, logic,
communications, graphics, etc.
Microprocessor
• A microprocessor (the most important chip) is
the miniaturised circuitry of a computer
processor-the part that processes data into
information. The microprocessor in a computer
is known as the CPU- Central Processing Unit.
CPU
• The brain of the computer - follows the
instructions of the software to manipulate data
into information.
• The CPU consists of two parts:
1. The Control Unit-tells the rest of the computer
system how to carry out a programs
instructions.
2. The Arithmetic/Logic Unit(ALU)-performs
arithmetic operations (addition, subtraction,
multiplication and division) and logic
operations (comparisons of two pieces of data
to see whether one is = to, > than or < than the
other) and controls the speed of those
operations.
• The capacities of the CPU are measured in
terms of Word Size – the number of bits that
may be manipulated or stored at one time by
the CPU. Eg an 8-bit computer (one with an 8bit-word processor) will transfer data within
each CPU chip itself in 8-bit chunks.
• Bit- each 0 or 1 is called a bit (binary digit)
• Byte-a group of 8 bits is called a byte and
each byte represents one character, digit, or
other value.
Main Memory
• RAM Chips- Main memory (known as RAM) is
contained on RAM chips. It is also known as
memory, primary storage, internal memory. It has
3 tasks:
1. Holds data for processing
2. Holds instructions (programs) for processing
data
3. Holds processed data (information) waiting
to be sent to an output or secondary storage.
• RAM contents are temporary-once computer is
off all data and programs contained within
RAM vanish.
• RAM capacity varies in different computersmore RAM means more data can be processed
at once and how big and complex the programs
are that can be used to process it.
RAM chips
• RAM - Random Access Memory - memory
that temporarily holds data and instructions
that will be needed shortly by the CPU.
• RAM is often mounted on a small circuit board
like SIMM (single inline memory module) has multiple RAM chips on one side or DIMM
(dual inline memory module) - has multiple
RAM chips on both sides
• The more RAM you have, the faster the
computer operates, and the better your
software performs
Types of RAM chips
• DRAM chips - dynamic random access
memory
• SRAM chips - static random access memory
• EDO RAM chips - extended data out random
access memory
ROM chips
• Read Only Memory - also known as
firmware - cannot be written on or erased by
the computer user without special equipment.
• ROM chips contain programs (special
instructions for basic computer operations such
as starting the computer) that are built in at the
factory.
Other forms of memory
• Cache Memory - a special high speed
memory area that the CPU can access quickly.
• Cache memory is used in computers with very
fast CPUs - most frequently used instructions
are kept in cache memory so the CPU can look
there first.
• This allows CPU to run faster as it doesn’t
have to take time to swap instructions in and
out of main memory.
• Video Memory - VRAM- these chips are used
to store display images for the monitor.
• The amount of video memory determines how
fast images appear and how many colours are
available.
• Flash Memory - Flash RAM - these cards
consist of circuitry on credit card sized cards
that can be inserted into slots connected to the
motherboard.
• Flash memory is non-volatile - that is, it retains
its data even when the power is switched off.
Registers
• Registers are used by the Control Unit and the
ALU to enhance the computer’s performance.
• They are high-speed storage areas that
temporarily store data during processing.
• Registers hold material that is to be processed
immediately.
• The computer loads the program instructions
and data from main memory into the registers
just before processing, which helps the
computer process faster.
• Types of registers are:
– instruction register,
– address register and
– storage register.
Addresses
• The computer keeps track of data and
instructions by using addresses (locations,
designated by a unique number in main
memory, in which a character of data or of an
instruction is stored during processing).
• To process each character, the control unit
retrieves that character from its address in
main memory and places it into a register. This
is the first step of the machine cycle.
Machine Cycle
• This cycle is a series of operations performed
to execute a single program instruction.
• The machine cycle consists of two parts:
• The Instruction Cycle: the control unit
fetches an instruction from main memory and
decodes that instruction.
• The Execution Cycle: the ALU executes the
instruction and stores the processed results in
main memory or a register.
• The entire machine cycle is synchronised by a
system clock - controls how fast all the
operations within a computer take place.
• The faster the system clock, the faster the
processing.
• Processing speeds are usually expressed in
megahertz(MHz) - 1 MHz equals one million
cycles per second.
Ways of measuring processing speeds
• Microcomputers - in megahertz (MHz)
• Workstations, minicomputers, mainframes measured according to the number of
instructions processed in one second – MIPS -millions of instructions per second
that the processor can perform
• Supercomputers - processor speed measured in
flops - floating-point operations (special kind
of mathematical calculation) per second.
• Can measure processing speeds in fractions of
a second.
– For older machines, speed for completing
one machine cycle is measured in
milliseconds.
– For microcomputers - microseconds
– For mainframes - nanoseconds
• A millisecond is one-thousandth of a second
• A microsecond is one-millionth of a second
• A nanosecond is one-billionth of a second
• A picosecond is one-trillionth of a second
Machine Language
• Machine language is a binary-type
programming language that the computer can
run directly.
• Special system programs called language
translators convert the instructions into
machine language - language that computers
can understand.
What makes up a computer?
• Microcomputer system unit - is the box or
cabinet that contains the electrical and
hardware components that make the computer
work.
• Components that make up the system unit are:
power supply, motherboard, CPU chip,
specialised processor chips, RAM & ROM
chips, other memory - cache, flash, VRAM,
expansion slots and boards, bus lines, ports, PC
slots and cards.
Power Supply
• A device that converts Alternating Current to
Direct Current to run the computer.
• Protection for the power supply comes in 3
forms:
– Surge Protector -a device that helps protect
a computer from being damaged by surges
of high voltage.
– Voltage Regulator -a device that protects a
computer from being damaged by
insufficient power eg brownouts or sags in
voltage.
– UPS - uninterruptible power supply - a
battery operated device that acts as a surge
protector and provides a computer with
electricity if there is a power failure.
Motherboard
• Also known as the system board -it is the main
circuit board in the system unit.
• Contains
– the CPU or microprocessor;
– RAM; and
– expansion slots where additional circuit
boards can be plugged in.
CPU Chip
• Most computers use two main types of CPU
chip or processor: Intel and Motorola.
• Intel chips are made principally by Intel
Corporation for PCs
• Motorola chips are made by Motorola for
Apple computers.
• CISC chips (complex instruction set
computing) - used mostly in PCs and in
mainframes
• RISC chips (reduced instruction set
computing) - used mainly in workstations such
as Sun Microsystems an Hewlett-Packard
Specialised processor chips
• A motherboard has slots for plugging in
specialised processor chips.
• Eg Maths coprocessor chips help programs
using lots of mathematical equations to run
faster
• Graphics coprocessor chips enhances the
performance of programs with lots of graphics
and helps create complex screen displays.
Expansion Slots and Boards
• All motherboards can be expanded - more
memory or peripheral devices can be added to
the motherboard.
• Expansion slots are sockets on the
motherboard into which expansion cards can
be plugged into.
• Expansion cards are circuit boards that
– provide more memory or
– control peripheral devices.
Types of Expansion Cards
• Expanded memory - allow you to add RAM
chips
• Display adaptor or Graphic adaptor cards allow you to adapt different kinds of colour
video display monitors for your computer.
• Controller Cards - allow your CPU to work
with the computers various peripheral devices.
• Other Add-Ons - you can add special circuit
boards for modems, fax, sound and
networking, as well as maths or graphics
coprocessor chips.
Bus Lines
• A bus line - bus - is an electrical pathway
through which bits are transmitted within the
CPU and between the CPU and other devices
in the system.
• Expansion Buses connect RAM with
expansion slots
• Local Buses avoid RAM and connect
expansion slots directly with the CPU.
• Other types of buses are address bus, control
bus and data bus.
Ports
• A port is a socket on the outside of the system
unit that is connected to a board on the inside
of the system unit.
• They allow you to plug in a cable to connect a
peripheral device eg monitor, printer, so that it
can communicate with the computer system.
Types of Ports
• Game ports - allow you to attach a joystick or
similar game playing device to the system unit
• Parallel ports - allow lines to be connected
that will enable 8 bits to be transmitted
simultaneously.
• Serial ports - RS 232 port - enables a line to
be connected that will send bits one after the
other ona single line.
• Video adaptor ports - used to connect the
monitor outside the computer to the video
adaptor card inside the system unit.
• SCSI ports - small computer systems interface
- provide an interface for transferring data at
high speeds for up to 7 or 15 compatible SCSI
devices such as external hard-drives, CD ROM
drives, etc.
• Infrared ports - allows a computer to make a
cable-less connection with infrared-capable
devices eg printers
• Universal Serial Bus - USB - allows up to 127
peripherals to be connected through just one
general-purpose port.
• USB 3.0 is the next generation of technology
of USB connection, which will allow higher
interface speeds.
• While this technology is still not ready for the
general public, it is expected to be ready by
2010.
• USB 3.0 is called "SuperSpeed USB" by some
because of its speed improvements over both
USB 2.0 and 1.1.
• USB 3.0 will offer transfer rates of 4.8
gigabytes per second.
• At this speed, USB 3.0 can transfer a 25
gigabyte file in approximately 70 seconds.
• That would have taken 9.3 hours for the first
generation USB 1.1 and 14 minutes for USB 2.
• Firewire ports are forms of a serial port that
make use of FireWire technology to transfer
data rapidly from one electronic device to
another.
• The FireWire port has been in common use
since 1995, when Apple, Inc. first began to
include the port on a number of digital
camcorders. Today, the FireWire port is used
on a number of other devices.
Future Developments
• Thousand megahertz processor chips processors have now been developed so far
that they have processing speeds of 4 gigahertz
or more compared to 500 megahertz in 1997.
• Superconductors - is a material that allows
electricity to flow through it without
resistance.
• Opto-Electronic Processing - tomorrow
computers might be opto-electronic ie a
computer using lasers, lenses and mirrors
would represent the on-and-off codes of data
with pulses of light.
• Nanotechnology - is a science based on using
molecules to create tiny machines to hold data
or perform tasks.
• Biotechnology - using DNA molecules scientists have been working on sending data
through DNA molecules. More data can be
transferred than through the traditional silicon
chip.
• Wearable computers - computers have been
developed to be able to be worn eg British
Telecom have developed Office on the Arm,
with screen, touch-pad and microphone on a
forearm cuff.
Homework
• Read Chapter 4 and supplement notes using
the chapter as a guide.
• Complete True/False, Multiple Choice,
Matching and Short Answer questions on
pages 247 and 248.