How Computers Work

1. How Computers Work Unit 1, Module 3: PC Hardware Components - Part 2

2. Temporary (primary storage, or memory) Temporarily holds data and instructions while processing them Faster to access than permanent storage Permanent (secondary storage) Storage Devices

3. Primary Storage Devices • Memory, or RAM, located on the motherboard and on other circuit boards • Volatile • Temp. memory • Nonvolatile (or ROM) memory • Memory that holds data permanently even when the power is turned off

4. Primary Storage Devices • Common types of boards that hold memory chips • SIMMs (single inline memory modules) • DIMMs (dual inline memory modules) • RIMMs (memory modules manufactured by Rambus, Inc.) • Which one is the most common type of memory used today?

5. RAM Chips

6. Types of RAM ModulesPin Sizes

7. Primary Storage Cache Memory • Cache speeds up memory access, or holding area for data or instructions that are accessed frequently • On newer CPU’s, cache is stored inside the CPU housing on a memory chip that sits very close to the CPU microchip • Older CPU’s use COAST(cache on a stick) which is memory module on the motherboard or it is stored on individual chip

8. Secondary Storage Devices • Permanently hold data, even when PC is turned off • Hard disks • Floppy disks • Zip drives • CD-ROMs

9. Hard Drive • Contains a platter that rotates at high speed. • An arm with sensitive read/write head reaches across the platters which enables writing new data and reading exiting data from the HD.

10. Hard Drive • Uses IDE (Integrated Drive Electronics) technology; can accommodate up to four EIDE devices on one system • IDE provides two connectors on a motherboard for two data cables • Motherboard can accommodate up to 4 IDE devices on one system…HD, Zip Drive, CD-ROM and tape Drives

11. Motherboard with Two IDE Connectors

12. A Typical System

14. Floppy Drive • Sizes 3.5 and the older 5.25 floppy drives • Requires a controller • Floppy drive cable allows attach two drives…Drive A at the end of the cable and Drive B in the middle of the cable • Electricity to a floppy drive is provided by a the power cord from the power supply

15. Floppy Drive

16. CD-ROM • Compact Disc Read Only Memory • Needs a power cord and IDE data cable

17. Motherboard Components Used for Communication Among Devices • Traces • Are circuits, or paths, that enable data, instructions, and power to move from component to component on the board • Represented by fine lines on both the top and the bottom of board’s surface • Traces are also referred as a Bus Lines

18. Bus Lines

19. Motherboard Components Used for Communication Among Devices • The bus • The ability of the CPU to communicate with the rest of the system • System of pathways used for communication to travel between devices. • The motherboard has more than one bus.

20. Motherboard Components Used for Communication Among Devices • The System Bus • Know as the (external bus), (expansion bus), (front side bus) or (memory bus) • The main bus on the motherboard that communicates with the CPU, Memory, and the Chip Set, and Expansion Slots • It is know as the external bus because it is outside the processor

21. Motherboard Components Used for Communication Among Devices • The system is bus is a expansion bus because it is a bus system that allows the processor to talk to another device which are connected to expansion slots. • Types of expansion slots • PCI (Peripheral Component Interconnect) • For high-speed input/output devices) • AGP (Accelerated Graphics Port) • For a video card • ISA (Industry Standard Architecture) • Used by older and/or slower devices)

22. System Clock • Found on a bus to Synchronizes activity on the motherboard • Sends continuous pulses carried on bus over the motherboard to chips, expansion slots to ensure that all activities are performed in a synchronized fashion • The clock single or pulses are generated by a quartz crystal located on motherboard • Frequency of activity is measured in Megahertz (MHz), or 1 million cycles per second

23. System Clock • CPU operates from 166 MHz to two GHz, or two thousand MHz (2 billion cycles per second.) • This means rate of speed that the processor executes commands is measured by the clock speed

24. Expansion Cards • Enable the CPU to connect to an external device or to a network are mounted in expansion slots on the motherboard • Cards can provide ports as well • Expansion cards include: sound, video, network, modem • Determine the the function of the card by looking at the port • Example: Video Card has 15 pins, 3 rows of pins

25. The Electrical System • Power supply • Converts AC power from the wall outlet into DC power that can be used by the computer. • Newer power supplies provide 3.3, 5 and 12 volts of DC. • Runs a fan directly from electrical output voltage to cool inside of computer case

26. Instructions and Data Stored on the Motherboard • ROM (read-only memory) chips store very basic instructions and data that are stored on motherboard • ROM chip has software instructions permanently etched into the chip is called Firmware • This type of memory is nonvolatile

27. Instructions and Data Stored on the Motherboard • BIOS (basic input/output system)chips • ROM Chips hold programs or software the tell CPU how to perform many input/output tasks. • Examples: • ROM BIOS chip on the motherboard contain programming to start up the PC and to perform other task such as interacting with Floppy Disk Drive

28. Instructions and Data Stored on the Motherboard • As new hardware components or BIOS features become available the ROM chips need to be upgraded or within the past needed to be replaced • Today…Flash ROM chips allows for ROM chips to be reprogrammed or changed without replacing the chips

29. Instructions and Data Stored on the Motherboard • CMOS chip • Also called CMOS RAM • CMOS contains data about the system configuration, current time and date • When computer turns on, it looks for the CMOS chip to find what hardware it should expect to find.

30. Instructions and Data Stored on the Motherboard • CMOS chip…continued • Powered by a battery on motherboard when power is off • CMOS chip is RAM but the chip retains its data • If battery dies setup info. is all lost • Access to a computer can be controlled by power-on password in CMOS by accessing the setup screen • Some computers provide a jumper near CMOS chip that when set to “On” causes the computer to forget any changes that have been made to default settings in CMOS or disable the password

31. SetupInstallation Information • Jumpers: two wires that stick up side by side on the system board that are used to hold configuration information. • The two pins and the connection together server as electrical connection on the motherboard • If the pins are not connected with a cover, the setting is considered “OFF” • If the cover is present, the setting is “ON”.

32. Jumpers

33. Dip Switches • Dual Inline Package Switch (DIP) • Like on a light switch that has on and off settings • Not found on new systems

34. Review • Storage within in a computer consists of primary and secondary storage. • Two types of memory exist within a computer: Volatile and nonvolatile. • BIOS provides instructions for your computer in order for it to boot. • Configurations settings are set by using jumpers and dip switches.