Components of a Computer System: The System Unit and Data Representation - Prof. Wooyoung , Study notes of Computer Science

Download Components of a Computer System: The System Unit and Data Representation - Prof. Wooyoung and more Study notes Computer Science in PDF only on Docsity! 1 Chapter 4 The Components of the System Unit The System Unit • Box-like case that contains computer’s electronic components • Sometimes called the chassis What are common components inside the system unit? • Processor • Memory module • Expansion cards o Sound card o Modem card o Video card o Network interface card • Ports and Connectors What is the motherboard? • Main circuit board in system unit • Contains chips, integrated circuits, and transistors • Also called system board What chip packages are available? • single edge contact (SEC) cartridge • dual inline package (DIP) • flip chip-PGA (FC-PGA) package • pin grid array (PGA Central Processing Unit What is the central processing unit (CPU) ? • Interprets and carries out basic instructions that operate a computer • Also called the processor What are the components of the CPU? • Control Unit • Arithmetic/Logic Unit (ALU) What is the control unit? • Directs and coordinates operations in computer • Control unit repeats four basic operations: 2 • Fetch - obtain program instruction or data item from memory • Decode - translate instruction into commands • Execute - carry out command • Store - write result to memory What is a machine cycle? • Four operations of the CPU comprise a machine cycle • Also called instruction cycle • Instruction time (i-time) - time taken to fetch and decode • Execution time (e-time) - time taken to execute and store An example of a machine cycle • Student enters math problem (100 x 52) into computer’s memory • Result in memory displays on monitor’s screen How is the CPU’s speed measured? • According to how many millions of instructions per second (MIPS) it can process What are two designs used for the CPU? • CISC (complex instruction set computing) o Supports large number of instructions o CPU executes complex instructions more quickly • RISC (reduced instruction set computing) o Supports smaller number of instructions o CPU executes simple instructions more quickly What is the arithmetic/logic unit (ALU) ? • CPU component that performs execution part of the machine cycle o Arithmetic (addition, subtraction, multiplication, and division) o Comparison (greater than, equal to, or less than) o Logical (AND, OR, NOT) What is pipelining? • CPU begins executing second instruction before completing first instruction • Results in faster processing What is a register? • Temporary storage area that holds data and instructions o Stores location from where instruction was fetched o Stores instruction while it is being decoded o Stores data while ALU processes it 5 What is cache • Helps speed computer processes by storing frequently used instructions and data • Also called memory cache, cache store, or RAM cache • L1 cache built in processor • L2 and L3 cache not built in processor • L2 advanced transfer cache most common What is read-only memory (ROM)? • Memory chips that contain data, instructions, or information that is recorded permanently • Data can only be read; cannot be modified in ROM • ROM is nonvolatile — Contents not lost when computer is turned off o BIOS (basic input/output system) o Stored on ROM • Sequence of instructions computer follows to load operating system and other files when you turn on the computer Types of ROM • Firmware • ROM chips manufactured with permanently written data, instructions, or information • PROM (programmable read-only memory) o Blank ROM on which you can place items permanently • EEPROM (electrically erasable programmable read-only memory) o Type of PROM containing microcode programmer can erase What is flash memory? • Nonvolatile memory that can be erased electronically and reprogrammed • Used with handheld computers and digital cameras, cellular phones, and automobile What is CMOS? • Complementary metal-oxide semiconductor memory • Stores information about the computer o type of disk drives o keyboard o monitor o current time and date • Uses battery to retain information when computer is turned off What is memory access time? • Speed at which processor can access data from memory directly 6 • Measured in nanoseconds (ns), which is 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 Expansion Cards What is an expansion slot? • An opening, or socket, where circuit board is inserted into motherboard • Expansion card inserted in expansion slot How are expansion cards used? What is Plug and Play? • Computer automatically can configure cards and other devices as you install them What is a PC card? • Credit card-sized device used to add capabilities to notebook computers • PCMCIA - Personal Computer Memory Card International Association • Uses include modem, additional memory, and storage o Memory – Type I o Modem – Type II o Hard Drive – Type III What is a flash memory card? • Adds memory to handheld computers, digital music players, cellular telephones, and similar devices Ports What is a port? • Connects external devices to system unit o keyboard port o USB port o serial port o monitor port o game port o network port o mouse port o parallel port o speaker port o microphone port What are different types of connectors? 7 What is a serial port? • Transmits one bit of data at a time • Used to connect slow-speed devices, such as mouse, keyboard, mode What is a parallel port? • Connects devices that can transfer more than one bit at a time, such as a printer What is a universal serial bus port (USB) ? • Connector that supports newer peripherals and plug and play • Can connect 127 devices • Other popular ports include 1394, MIDI, SCSI, and IrDA Buses What is a bus? • Channel that allows devices inside computer to communicate with each other • On the motherboard • System bus connects processor and RAM • Bus width determines number of bits transmitted at one time • Word size determines number of bits processor can interpret and execute at a given time o Usually same as bus width What is an expansion bus? • Allows processor to communicate with peripherals o ISA – most common, slowest o Local Bus – high-speed, connects higher speed devices o AGP – designed by Intel to improve 3-D graphics Bays What is a bay? • Open area inside system unit used to install additional equipment Power Supply What is a power supply? • Converts alternating current (AC) to direct current (DC) • Some peripheral devices have AC adapter Mobile Computers What is a mobile computer? • Notebook, which weighs between 2.5 and 8 pounds, or handheld What ports are on a notebook computer?