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 circuits-circuits 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 8-bit-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 processing2. Holds instructions (programs) for processing

data3. 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 computers-more 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.

• 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.

Future Developments

• 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.