Chapter 4 The Components of the System Unit System unit: Case that contains electronic components power supply ports drive bays processor memory sound card video card modem card network card Chapter 4: System Unit

Motherboard Main circuit board in system unit processor chip adapter cards memory chips memory slots motherboard Expansion slots for adapter cards Main circuit board in system unit Contains adapter cards, processor chips, and memory chips Chapter 4: System Unit p. 128 Fig. 4-3 Next

Arithmetic Logic Unit (ALU) Processor Processor Control Unit Arithmetic Logic Unit (ALU) CPU Interprets and performs basic instructions Control unit: coordinates operations ALU: performs math functions Control Unit Arithmetic Logic Unit (ALU) Instructions Data Information Memory Input Devices Data Information Output Devices Instructions Data Information Storage Devices Chapter 4: System Unit p. 128 Fig. 4-4 Next

Pace of system clock is clock speed Controls timing of all computer operations Generates regular electronic pulses that set operating pace 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) Chapter 4: System Unit p. 130 Next

Processor Faster processor, more expensive Click to view video Chapter 4: System Unit p. 131 Next

Data Representation How do computers represent data? Recognize only two discrete states: on or off Use a binary system to recognize two states Bytes: eight bits Chapter 4: System Unit p. 132 Fig. 4-6 Next

Data Representation What is a byte? Eight bits grouped together as a unit Provides enough different combinations of 0s and 1s to represent 256 individual characters What is a byte? Chapter 4: System Unit p. 132 Fig. 4-7 Next

Data Representation What are three popular coding systems to represent data? ASCII— personal computers EBCDIC—mainframes ASCII Symbol EBCDIC 00110000 0 11110000 00110001 1 11110001 00110010 2 11110010 00110011 3 11110011 Chapter 4: System Unit p. 132 Fig. 4-8 Next

Memory Seat #2B4 Seat #2B3 What is memory? Electronic components store instructions, data, and results Consists of chips on motherboard Each byte stored in unique location called an address Chapter 4: System Unit p. 134 Fig. 4-10 Next

Memory How is memory measured? By number of bytes available for storage Term Abbreviation Approximate Size Kilobyte KB or K 1 thousand bytes Megabyte MB 1 million bytes Gigabyte GB 1 billion bytes Terabyte TB 1 trillion bytes Chapter 4: System Unit p. 134 Fig. 4-11 Next

Memory What is random access memory (RAM)? Most RAM is volatile, it is lost when computer’s power is turned off Memory chips that can be read from and written to by processor The more RAM a computer has, the faster it responds Click to view Web Link, click Chapter 4, Click Web Link from left navigation, then click RAM below Chapter 4 Chapter 4: System Unit p. 135 Next

Memory How much RAM does an application require? System Requirements Windows® XP Home Edition/Professional Intel Pentium processor at 233MHZ or higher AMD K6 (Athlon Duron Family processor at 233MHZ or higher 64 MB of RAM Software package indicates RAM requirements For optimal performance, need more than minimum specifications Chapter 4: System Unit p. 136 Fig. 4-14 Next

Memory What is cache? Helps speed computer processes by storing frequently used instructions and data L1 cache built into processor L2 cache slower but has larger capacity Chapter 4: System Unit p. 137 Next

Memory What is read-only memory (ROM)? The data on most ROM chips cannot be modified Memory chips that store permanent data and instructions Chapter 4: System Unit p. 137 Next

Memory What is flash memory?’ Nonvolatile memory that can be erased electronically and reprogrammed Click to view Web Link, click Chapter 4, Click Web Link from left navigation, then click Flash Memory below Chapter 4 Chapter 4: System Unit p. 137 Fig. 4-15 Next

Stores date, time, and computer’s startup information Memory What is CMOS? Uses battery power to retain information when other power is turned off Stores date, time, and computer’s startup information Chapter 4: System Unit p. 139 Next

Expansion Slots and Adapter Cards What is an expansion slot? An opening, or socket, on the motherboard that can hold an adapter card Chapter 4: System Unit p. 140 Fig. 4-19 Next

Ports and Connectors What is a serial port? Transmits one bit of data at a time Connects slow-speed devices, such as mouse, keyboard, modem Chapter 4: System Unit p. 142 Fig. 4-23 Next

Ports and Connectors What is a parallel port? Connects devices that can transfer more than one bit at a time, such as a printer Chapter 4: System Unit p. 142 Fig. 4-24 Next

USB (universal serial bus) port Ports and Connectors USB (universal serial bus) port What are USB ports? PCs typically have four to eight USB ports on front or back of the system unit Latest version is called USB 2.0 Can be used to attach multiple peripherals Chapter 4: System Unit p. 142 Next

Buses What is a bus? Channel allows devices to communicate with each other Connects processor and RAM Access times… RAM, hard drive, floppy Click to view Web Link, click Chapter 4, Click Web Link from left navigation, then click Buses below Chapter 4 Chapter 4: System Unit p. 144 Fig. 4-25 Next