hardware processors a bit of history in the 40’s the first computer (eniac) used vacuum tubes to...
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Hardware
Processors
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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.
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• 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.
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• Chips contain millions of micro-miniature electronic circuit components, mainly transistors. There are different kinds of chips eg microprocessor, memory, logic, communications, graphics, etc.
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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.
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CPU
• The brain of the computer - follows the instructions of the software to manipulate data into information.
• The CPU consists of two parts:
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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.
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• 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.
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• 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.
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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.
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• 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.
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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
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• The more RAM you have, the faster the computer operates, and the better your software performs
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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
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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.
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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.
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• 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.
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• 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.
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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.
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• 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.
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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.
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Machine Cycle
• This cycle is a series of operations performed to execute a single program instruction.
• The machine cycle consists of two parts:
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• 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.
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• 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.
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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
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• 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
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• 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
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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.
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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.
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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.
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– 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.
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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.
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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.
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• 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
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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.
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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.
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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.
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• 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.
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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.
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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.
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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.
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• 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.
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• 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.
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• 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.
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• 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.
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• 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.
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• 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
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• 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.
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• 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.
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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.