THE SYSTEM UNIT
Discovery Computers 2005 Chapter 4
nSystem unit
–Common components
»Motherboard with Processor
»Memory module
»Expansion cards
»Ports
»Connectors
CPU AND MICROPROCESSOR
nCPU (processor)
–Interprets and carries out the basic instructions that operate a computer
–Microprocessor
»Pentium processor
nThe Control Unit
–A component of the CPU that directs and coordinates most of the operations in the computer
CPU AND MICROPROCESSOR
nThe Arithmetic/Logic Unit
–Performs the execution part of the machine cycle
–Arithmetic (addition, subtraction, multiplication, division)
–Comparison (greater than, equal to, less than)
–Logical (AND, OR, NOT)
–Speed is measured in MIPS
CPU AND MICROPROCESSOR
nMachine Cycle
»Fetch - get the next instruction from memory
»Decode - translate the instruction
»Execute - carry out the command
»Store - write the result to memory
nPipelining
–The CPU begins execution of a second instruction before the first instruction is completed
–Faster processing
CPU AND MICROPROCESSOR
nMicroprocessor Comparison
–Intel Pentium
–Intel Celeron
–AMD (Intel-compatible)
–Motorola PowerPC
–Alpha
nProcessor Installation and Upgrades
–Zero-insertion force (ZIF) sockets
–Upgrades
»Chip for chip
»Piggyback
»Daughterboard
CPU AND MICROPROCESSOR
nHeat Sinks and Heat Pipes
–Heat sink
»Small ceramic or metal component with fins on its surface that is designed to absorb and ventilate heat produced by electrical components
–Heat pipe
»Like a heat sink, but used in laptops
CPU AND MICROPROCESSOR
nCoprocessors
–Special processor chip or circuit board designed to assist the processor in performing specific tasks
–Floating-point coprocessor
nParallel Processing
–Using multiple processors simultaneously to execute a program
–Speeds execution
–Requires special software
DATA REPRESENTATION
nASCII vs. EBCDIC
–Sufficient for English and Western European languages
–Unicode often used for others
nUNICODE
Machine Language & Cycle
MEMORY
nSize of memory is measured by the number of bytes available
–Kilobyte - 1,024 bytes
–Megabyte - one million bytes
nTwo memory types
–Volatile
–Nonvolatile
MEMORY
nRAM
–Random access memory
–The memory chips in the system unit
–When the computer starts, operating system files are loaded from a hard disk into RAM
nRAM (contd.)
–Dynamic RAM (DRAM)
–Synchronous DRAM (SDRAM)
–Rambus DRAM (RDRAM)
–Static RAM (SRAM)
System Memory
nCache
Memory
–Throughput
nROM
nPROM,
EEPROM
nFlash
Memory
EXPANSION SLOTS AND EXPANSION CARDS
nAn opening, or socket, where a circuit board can be inserted into the motherboard
nAdd new devices or capabilities to the computer
nThree common types
–Video card
–Sound card
–Internal modem
nPlug and Play
EXPANSION SLOTS AND EXPANSION CARDS
nPC Cards
–Used on laptops and other portable computers
–Credit card-sized
–Personal Computer Memory Card International Association (PCMCIA)
–Thickness of card varies
»Type I, II, III
–Often, can be hot swapped
PORTS
nUsed to connect external devices to the system unit
–Most located on the back of the system unit
–Many types of connectors
nUsed to connect external devices to the system unit
–Most located on the back of the system unit
–Many types of connectors
–Some connectors are on the computer when purchased, others added with expansion slots
PORTS
nSerial Ports
–Transmits one bit of data at a time
–Used to connect devices that do not require fast transmission rates
»Mouse, Keyboard, Modem
–Two common types
»25-pin and 9-pin
nParallel Ports
–Connect devices that can transfer more than one bit at a time
–Usually used for printers
–Two newer types
»EPP
(Enhanced
»ECP
(Extended
PORTS
nSpecial-Purpose Ports
–USB – connect upto 127 devices
–
–
–1394 Port (FireWire)
–
»FIR (fast infrared)
BUSES
nAllow various devices inside the computer to communicate with each other
nBus width determines the number of bits transmitted at one time
nExpansion Bus
–Bus type determines type of expansion card you can add
–ISA
–Local bus
»VESA
»PCI
–Accelerated
–Universal Serial Bus (USB)
–PC Card bus
BAYS
nAn open area inside the system unit used to install additional equipment
nDrive bays
–Used for disk drives
–External drive bay
»Accessible from outside the system unit
–Internal drive bay
»Hidden entirely within the system unit