The Components of the System Unit

Transcription

1 Objectives Differentiate among various styles of system units Differentiate among the various types of memory The Components of the System Unit Identify chips, adapter cards, and other components of a motherboard Describe the components of a processor and how they complete a machine cycle Identify characteristics of various personal computer processors on the market today Define a bit and describe how a series of bits represents data Describe the types of expansion slots and adapter cards Explain the differences among a serial port, a parallel port, a USB port, a FireWire port, and other ports Describe how buses contribute to a computer s processing speed Identify components in mobile computers and mobile devices From Discovering Computers: Living in a Digital World Explain how programs transfer in and out of memory Understand how to clean a system unit 2 What is the system unit? Case that contains electronic components of the computer used to process data Sometimes called the chassis What are common components inside the system unit? Adapter cards Sound card Video card Drive bays Power supply 3 4 What is the motherboard? Main circuit board of the system unit Contains expansion slots, processor chips, and memory slots Also called system board What is a chip? Small piece of semi-conducting material on which integrated circuits are etched Integrated circuits contain many microscopic pathways capable of carrying electrical current Chips are packaged so they can be attached to a circuit board Next 5 6 1

2 What is the central processing unit (CPU)? Interprets and carries out basic instructions that operate a computer Control unit directs and coordinates operations in computer Arithmetic logic unit Input (ALU) performs Devices arithmetic, comparison, and logical operations Also called the processor Control Unit Data Instructions Data Information Arithmetic Logic Unit (ALU) Information Instructions Data Information Output Devices What is a machine cycle? Four operations of the CPU comprise a machine cycle Step 4. Store Write result to memory ALU Step 3. Execute Carry out command Step 1. Fetch Obtain program instruction or data item from memory Control Unit Step 2. Decode Translate instruction into commands Storage Devices 7 8 What is pipelining? begins fetching second instruction before completing machine cycle for first instruction Results in faster processing The processor contains registers, that temporarily hold data and instructions. A Register is a temporary high-speed storage area that holds data and instructions Stores instruction while it is being decoded Stores location from where instruction was fetched Stores results of calculation Stores data while ALU computes it 9 10 What is the system clock? Controls timing of all computer operations Generates regular electronic pulses, or ticks, that set operating pace of components of system unit Each tick is a clock cycle Pace of system clock is clock speed Most clock speeds are in the gigahertz (GHz) range (1 GHz = one billion ticks of system clock per second) speed can also be measured in millions of instructions per second (MIPS) What are dual-core and multi-core processors? A dual-core processor is a single chip that contains two separate processors A multi-core processor is a chip with two or more separate processors Each processor on a dual-core/multi-core chip generally runs at a slower clock speed, but increase overall performance

3 The leading manufacturers of personal computer processor chips are Intel and AMD Determine how you plan to use a new computer before selecting a processor A processor chip generates heat that could cause the chip to burn up. The following are used to reduce the heat: Heat sink component with fins that cools processor Heat pipee smaller device for notebook computers Liquid cooling uses a continuous flow of fluids to transfer heat away Data Representation Analog signals are continuous and vary in strength and quality Digital signals are in one of two states: on or off Most computers are digital The binary system uses two unique digits (0 and 1) Next Data Representation A computer circuit represents the 0 or the 1 electronically by the presence or absence of an electrical charge Eight bits grouped together as a unit are called a byte. A byte represents a single character in the computer Data Representation What are three popular coding systems to represent data? ASCII American Standard Code for Information Interchange EBCDIC Extended Binary Coded Decimal Interchange Code Unicode coding scheme capable of representing all world s languages ASCII Symbol EBCDIC

4 Data Representation How is a letter converted to binary form and back? Step 4. After processing, the binary code for the capital letter T is converted to an image, and displayed on the output device. T Step 1. The user presses the capital letter T (SHIFT+T key) on the keyboard. Step 3. The system unit converts the scan code for the capital letter T to its ASCII binary code ( ) and stores it in memory for processing. Step 2. An electronic signal for the capital letter T is sent to the system unit. What is memory? Electronic components that store instructions, data, and results Consists of one or more chips on motherboard or other circuit board Each byte stored in unique location called an address, similar to seats in a concert hall How is memory measured? By number of bytes available for storage Name Abbreviation Number of Bytes Relative Size Byte B 1 byte Can hold one character of data. Kilobyte KB 1,024 bytes (2 10 bytes) Can hold 1,024 characters or about half of a doublespaced typewritten page. Megabyte MB 1,048,576 bytes (2 20 bytes) Can hold approximately 768 pages of typed text. Gigabyte GB 1,073,741,824 bytes (2 30 bytes) Terabyte TB 1,099,511,627,776 bytes (2 40 bytes) Petabyte PB 1,125,899,906,842,62 bytes (2 50 bytes) Exabyte EB Zettabyte ZB 1,152,921,504,606,846,976 bytes (2 60 bytes) 1,180,591,620,717,411,303,424 bytes (2 70 bytes) Approximately 786,432 pages of text; 500 sheets of paper is approximately 2 inches, so this represents a stack of paper 262 feet high. This represents a stack of typewritten pages almost 51 miles high. The stack of pages is now 52,000 miles high, or approximately one-fourth the distance from the Earth to the moon. The stack of pages is now 52 million miles high, or just about twice the distance between the Earth and Venus. The stack of pages is now 52 billion miles high, some 20 times the distance between the Earth and Pluto. The system unit contains two types of memory: Volatile memory Loses its contents when power is turned off Example includes RAM Nonvolatile memory Does not lose contents when power is removed Examples include ROM, flash memory, and CMOS What is random access memory (RAM)? chips that can be read from and written to by processor Also called main memory or primary storage Most RAM is volatile, it is lost when computer s power is turned off The more RAM a computer has, the faster it responds Three basic types of RAM chips exist: Dynamic RAM (DRAM) Static RAM (SRAM) Magnetoresistive RAM (MRAM)

5 RAM chips usually reside on a memory module and are inserted into memory slots How much RAM do you need? Depends on type of software you intend to use on your computer What is memory cache? Helps speed computer processes by storing frequently used instructions and data What is read-only memory (ROM)? chips that store permanent data and instructions Nonvolatile memory, it is not lost when computer s power is turned off Click to view Web Link, click Chapter 4, Click Web Link from left navigation, then click Cache below Chapter p. 201 Fig L1 cache built into processor L2 cache slower but has larger capacity L2 advanced transfer cache is faster, built directly on processor chip L3 cache is separate from processor chip on motherboard (L3 is only on computers that use L2 advanced transfer cache) 27 Firmware Manufactured with permanently written data, instructions, or information Three types: EEPROM (electrically erasable programmable read-only memory) Type of PROM containing microcode programmer can erase PROM (programmable read-only memory) Blank ROM chip onto which a programmer can write permanently 28 What is access time? Amount of time it takes processor to read data from memory Measured in nanoseconds (ns), one billionth of a second It takes 1/10 of a second to blink your eye; a computer can perform up to 10 million operations in same amount of time Expansion Slots and Adapter Cards An expansion slot is a socket on the motherboard that can hold an adapter card An adapter card enhances functions of a component of the system unit and/or provides connections to peripherals Sound card and video card

6 Expansion Slots and Adapter Cards What is an expansion slot? An opening, or socket, on the motherboard that can hold an adapter card With Plug and Play, the computer automatically configures cards and other devices as you install them Expansion Slots and Adapter Cards What are flash memory cards, PC cards, and ExpressCard modules? An ExpressCard module adds memory, storage, sound, fax/modem, communications, and other capabilities to notebook computers A flash memory card allows users to transfer data from mobile devices to desktop computers USB Flash drive An PC card adds various capabilities to computers What are ports and connectors? Port connects external devices to system unit A port is the point at which a peripheral (external devices ) attaches to or communicates with a system unit (sometimes referred to as a jack) Connector joins cable to a port Available in one of two genders: male and female On a notebook computer, the ports are on the back, front, and/or sides What is a serial port? Transmits one bit of data at a time Connects slow-speed devices, such as mouse, keyboard, modem

7 What is a parallel port? Connects devices that can transfer more than one bit at a time, such as a printer A Universal Serial Bus (USB) port can connect up to 127 different peripherals together with a single connector You can attach multiple peripherals using a single USB port with a USB hub A port replicator is an external device that provides connections to peripherals through ports built into the device A docking station is an external device that attaches to a mobile computer or device Buses What is a bus? Channel that allows devices inside computer to communicate with each other System bus connects processor and RAM Bus width determines number of bits transmitted at one time Word size is the number of bits processor can interpret and execute at a given time Bays A bay is an opening inside the system unit in which you can install additional equipment A drive bay typically holds disk drives Keeping Your Computer or Mobile Device Clean Clean your computer or mobile device once or twice a year Turn off and unplug your computer or mobile device before cleaning it Use compressed air to blow away dust Use an antistatic wipe to clean the exterior of the case and a cleaning solution and soft cloth to clean the screen Over time, the system unit collects dust even in a clean environment Preventative maintenance requires a few basic products