Module 2 How Computers Work

Basic Functions of an Operating Systems Input – recognizing input from the keyboard or mouse Processing –- manipulating data according to the user's instructions Output – sending output to the video screen or printer Storage – keeping track of files for use later; examples of storage devices include floppy disks and hard drives.

Bootstrap For an operating system to run, it must be loaded into the computer's Random Access Memory (RAM). When a computer is first turned on, it launches a small program called the bootstrap loader that is located on the BIOS chip on the motherboard. The bootstrap's primary functions are to test the computer's hardware and to locate and load the operating system into RAM.

Power-On Self Test To test the computer's hardware, the bootstrap program runs a program called power-on self-test or POST. In this test, the computer's Central Processing Unit (CPU) checks itself first and then checks the computer's system timer. The POST checks the Random Access Memory (RAM) by writing data to each RAM chip and then reading that data. Any difference indicates a problem. If the POST finds errors, it sends a message to the computer monitor. If the POST finds errors that cannot be displayed on the monitor, it sends errors in the form of "beeps." The POST sends one beep and the screen begins to display OS loading messages once the bootstrap has determined that the computer has passed the POST.

Generic Cold Boot Sequence

Desktop / Tower Models

Power Floppy disk drive CD-ROM drive Hard disk drive LEDs NIC Video card Audio card Parallel port Serial port Mouse Port Tower Models

Power Supplies Converts AC to DC Converts AC to DC Typically 250 –300 watts Typically 250 –300 watts AT AT P8 & P9 connector 12 pin +5, -5, +12, -12 ATX ATX P1 connector 20 pin (keyed) +3.3,+5, -5, +12, -12

Cooling Systems The power supply fan helps prevent the computer components from overheating by maintaining airflow in the case. The power supply fan helps prevent the computer components from overheating by maintaining airflow in the case. Overheating is a critical problem that can cause a computer system to malfunction or fail. Overheating is a critical problem that can cause a computer system to malfunction or fail. A heat sink is made of a material that absorbs the heat generated. A heat sink is made of a material that absorbs the heat generated.

Motherboards System board / main board is crucial because it is the nerve center of the computer system. Everything else in the system plugs into it, is controlled by it, and depends on it to communicate with other devices on the system. It generally houses the CPU, the controller circuitry, the bus, RAM, expansion slots for additional boards, and ports for external devices. In addition, it contains the CMOS and other ROM BIOS and support chips providing varied functionality.

Motherboard Form Factors Describe their physical dimensions. AT ATX The ATX motherboard is similar to the Baby AT motherboard, except for a number of important enhancements. Most new systems come with the ATX motherboard form factor.

Motherboard Components The major components on the motherboard include: chipset – interconnects all the devices on the motherboard CPU socket expansion sockets I/O support BIOS RAM sockets power supply socket CMOS chip dip switches and jumpers memory cache

The Motherboard

Power Supply Hard (C) Drive Floppy (A) Drive CD (D) Drive Inside the Computer

Video Card Sound Card Motherboard Back Plane Card Processor RAM Speaker

DIMM memory slots ISA slot joystick connector IDE connectors PCI slots hard drive CD Drive power connector Floppy connector printer connector Mouse and keyboard connector USB ports processor (ZIF) socket chipset AMR slot AGP slot

Expansion Slots ISA slot PCI slots AMR slot AGP slot ISA – Industry Standard Architecture AMR – Audio/Modem Riser AGP – Accelerated Graphics Port PCI – Peripheral Component Interconnect

Dual Processor Motherboard DIMM memory slot IDE connectors PC bus slots hard drive CD Drive power connector Floppy connector system board IC VESA slot keyboard connector ISA slots PCI slot COM 1 COM 2 parallel port PRT 1 SIMM memory slots processor (ZIF) socket

system RAM IDE connectors hard drive CD Drive Floppy connector System board IC Expansion slots ISA slot PCI slots AMR slot AGP slot PS/2 or Mini-Din keyboard mouse USB Com 1 Com 2 parallel port/PRT 1 game port speaker line-in mic power connector

RJ-45USB 1/8” Stereo Phone Jacks DB-15 – Serial Port DB-9 – Com 1 and Com 2 DB-15 – Video PortPS/2 - Mini Din – Keyboard and Mouse

Central Processing Units

Central Processing Unit Most important elements of the personal computer. On the motherboard, the CPU is contained on a single integrated circuit called the microprocessor. The computer will not run without a CPU. Often referred to as the brains of a computer, the CPU contains two basic components: Control unit Arithmetic/Logic Unit (ALU)

Control Unit Instructs the rest of the computer system on how to follow a program's instructions. It directs the movement of data to and from processor memory. The control unit temporarily holds data, instructions, and processed information in its arithmetic/logic unit. In addition, it directs control signals between the CPU and external devices such as hard disks, main memory, I/O ports, etc.

Processor Speed CPU descriptions as Pentium 133, Pentium 166, or Pentium 200 are well known. These numbers are specifications that indicate the maximum (reliable) operating speed at which the CPU can execute instructions. The CPU speed is not controlled by the microprocessor itself, but by an external clock located on the motherboard. The speed of the processor is determined by the frequency of the clock signal. Typically expressed in megahertz (MHz), and the higher the number, the faster the processor.

BIOS ROM The basic input/output system (BIOS) contains the instructions and data in the ROM chip that control the boot process and the computer hardware. BIOS is sometimes called firmware. The ROM chip that contains the firmware is called the ROM BIOS chip, ROM BIOS, or simply BIOS.

AGPAGP Expansion Cards Network card Modem card Sound card Video card

Expansion Slots Sockets, are receptacles on the computer motherboard that accept printed circuit boards. They allow additional devices to be added. Examples include video cards, I/O cards, and sound cards. Common expansion slots: Industry Standard Architecture (ISA ) – 8 MHz, 16-bit Peripheral Component Interconnect (PCI ) – 33 MHz, 32 and 64- bit Accelerated Graphics Port (AGP) - video adapters – 32-bit

Riser Cards Riser card CNR AMR

Riser Cards

System Buses

RAM – Random Access Memory (SIMMS / DIMMS / RIMMS)

RAM – Random Access Memory (SIMMS / DIMMS Installation)

Cache Memory L1 cache is located on the CPU. L2 cache is located between the CPU and DRAM. L1 cache is faster than L2 because it is located within the CPU and runs at same speed as the CPU. It is the first place the CPU looks for its data. If data is not found in L1 cache, the search will then continue with L2 cache, and then on to main memory. COASt modules are used to provide cache memory on many Pentium-based systems.

Monitors Computers are usually connected to a display, also called a monitor. Some key monitor-related terms are: pixels, refresh rate, resolution, and size. Measure screen size diagonally. Pixels – Are picture elements. The screen image is made of pixels (tiny dots), which are arranged in rows across the screen. Each pixel consists of three colors: red, green, and blue (RGB). Dot pitch – A measurement of how close together the phosphor dots are on the screen. The finer the dot pitch, the better image quality (measured in millimeters).

CRT – Cathode Ray tube LDC – Liquid Crystal Display Cable technology - VGA and DVI are the two most common. Viewable area (usually measured diagonally) Aspect ratio and orientation (landscape or portrait) Maximum resolution Dot pitch - Refresh rate - Color depth Amount of power consumption Display Technology

Dot Pitch

Refresh Rate, Measured in Hertz (Hz)

Changing Your Screen Resolution

CRT A cathode-ray tube is a special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube. The beam of electrons leaves a bright spot wherever it strikes the phosphor screen.

Video Card video BIOS video controller IC video RAM

Ports USB DB9 COMPortsCOMPorts Firewire DB25--parallel SCSI Mini-DIN Game Port-DB15 PORTS

I /O Ports All peripheral devices that connect to the computer such as printers, scanners, and so on, use connectors on the back of the computer known as ports. Ports: Serial ports – 1 bit at a time (9 pin male) Parallel ports – 1 byte at a time USB (Universal serial bus) – 127 devices daisy chained, hot swappable, 450 Mbps Modem - RJ11 connectors NIC – RJ45 connectors Firewire – 63 devices using cable lengths up to 4.5 m, 400Mbps

Serial Ports A serial port can be used to connect devices that use a serial interface such as a modem, scanner, mouse, etc. Generally, a PC can identify up to four serial ports, but the typical computer contains only two, referred to as COM1 and COM2. A serial port transmits data bits one after the other (serially) over a single line.

Parallel Ports A parallel port is a socket on the computer that is used to connect a printer or other peripheral device such as a portable hard disk, tape backup, scanner, or a CD-ROM. The parallel port contains eight lines for transmitting an entire byte (8 bits) across the eight data lines simultaneously. Parallel ports can be configured as LPT1 (IRQ 7) LPT2 (IRQ 5)

PS/2 Ports PS/2 keyboard or PS/2 mouse ports (Mini-DIN) are used to connect your PC to its keyboard and mouse. Both ports look identical, ports are not interchangeable. Mouse (green) Keyboard (purple). Usually both ports are color coded or labeled to avoid any confusion.

USB – Universal Serial Bus 127 devices 127 devices Transfer rate up to 12 Mbps Transfer rate up to 12 Mbps USB 2.0 up to 450 Mbps USB 2.0 up to 450 Mbps USB keyboards Mice Printers Modems Scanners Digital cameras Digital video cameras External disk drives

EIDE and SCSI Controllers The internal hard drive is connected to a disk controller with a cable—a 40 pin cable. The hard drive and other devices can use one of two types of interface controllers to work with the computer. These include the Enhanced Integrated Drive Electronics (EIDE), and Small Computer System Interface (SCSI, pronounced "scuzzy") connections.

EIDE Controllers Enhanced IDE (EIDE) is the "new and improved" Integrated Drive Electronics (IDE) drive interface. Not confined to IDE's 528 MB of data, the EIDE interface can handle up to 8.4 GB or more. While IDE can support only two drives, EIDE can support up to four devices using two IDE cables.

SCSI Controllers Small Computer System Interface Like EIDE, SCSI devices have the controlling electronics on each of the drives. A standard SCSI interface will allow up to 7devices to be connected to one SCSI adapter or controller. If the SCSI card is counted, it makes eight SCSI devices. Such devices may include hard drives, CD-ROM drives, taped drives, scanners, and removable drives. Each SCSI device in the chain, including the SCSI controller card is given a SCSI ID number from 0 to 7; #0 for the primary boot device (hard drive), and #7 for the SCSI controller card.

SCSI continued..

Hard Disk Drive The HDD has a much larger storage capacity than the floppy for long-term storage. It stores your programs and files, as well as the operating system. Typically, the HDD is an internal drive that cannot be removed from the computer.

Hard Disk Drive Components Disk platters, read/write heads, head actuator assembly, spindle motor, logic/circuit board, bezel/faceplate, configuration jumpers, and interface connectors. Disk platters are the actual media on which data is stored in the hard disk drive. Read/write heads are used to access the media. The disk platters require a read/write head for each side. Spindle motor which spins the platters.

Floppy Disk Drive 3.5” 3.5” 1.44 MB storage 1.44 MB storage Write Protect Write Protect

CD ROM Secondary Storage Device Secondary Storage Device CD-ROM Speed indicated by x (multiples of 150 kbps) CD-ROM Speed indicated by x (multiples of 150 kbps) CR-ROM – Read Only CD-R – Record able CD-RW – Record able & rewrites 650 – 700 MB 650 – 700 MB 52x/32x/52x 52x/32x/52x W /RW/R W /RW/R

DVD – Digital Video Disk Storage Capacity 25 times more than CDs Storage Capacity 25 times more than CDs DVD-R DVD-R DVD-RW DVD-RW

NIC –Network Adapter Card Network Interface Network Interface Token Ring Ethernet RJ-45 RJ-45

Modem uses Dial Up Network connection uses Dial Up Network connection converts digital data into analog converts digital data into analog modulates/demodulates modulates/demodulates 56 Kbps 56 Kbps RJ-11 connectors RJ-11 connectors UART chip—16550 UART chip—16550 V.92 current standard V.92 current standard

Interrupt Request “Hey CPU wake up and process this.” Modern computers and operating systems owe their reliability to the organized way in which they handle internal transactions. Various hardware devices, for example, may want to tell the CPU that they have some information available that is ready for transfer. The devices indicate this by making an interrupt request, or IRQ. It is a general rule that IRQs CANNOT be shared.

Interrupt Request

Direct Memory Access (DMA) Channels allow devices to bypass the processor and directly access the computer memory. Devices with a DMA channel assignment, as a result, gain the advantage of faster data transfers. DMA channels are typically used by high-speed communication devices for transferring large amounts of data at high speeds. Examples of such devices include sound cards, some network cards, some SCSI cards, some disk drives, and some tape backup drives.

DMA Channels

I /O Address In addition to an IRQ, computer components also need to be assigned an I/O port number. An I/O port number is a memory address where data is temporarily stored as it moves in and out of the devices. The I/O address is very similar to a post office box.

I /O Address FF-EE-77-8 Frequently referred to I / O Addresses: 3F8 = COM1 2F8 = COM2 3E8 = COM3 2E8 = COM4 378 = LPT1 278 = LPT2

Laptop Computers / Batteries / LCD Displays

PCMCIA Cards Personal Computer Memory Card Interface Association Type I Type I 3.3 mm memory Type II Type II 5.0 mm NIC, modem, etc. Type III Type III 10.5 mm Hard drives

Docking Station Collection of devices: Collection of devices: Monitor AC Power Network Connection Keyboard Mouse Printer

Wireless Access Points Allows computer to go anywhere within a range Allows computer to go anywhere within a range Wired controller receives and transmits data to wireless adapter Wired controller receives and transmits data to wireless adapter 802.x 802.x A B G

Q:How many devices will SCSI 1 support? A:7 devices Q:How many devices will SCSI 2 support? A:16 devices Q:How can I measure a monitor and what are the colors associated with a monitor? A:Diagonally, Red-Green-Blue Q:What is a warm boot? A:Restarting the computer, Ctrl-Alt-Del Q:What is the very first thing that POST checks? A:CPU then memory Q:Does the external clock on the motherboard determine the speed of the CPU? A:Yes Let’s see what you have learned...

Q:What type of processor uses Slot A on a motherboard? A:AMD Q:What is AGP? A:Accelerated Graphics Port, Used for Video adapters Q:What expansion slot runs at 33 MHz? A:PCI – Peripheral Component Interconnect Q:How many pins are there in a SIMM module? A:72 pins Q:How many pins are there in a DIMM module? A:168 pins

Q:What type of memory is commonly used as cache? A:SRAM – Synchronous Random Access Memory Q:Is a USB device hot swappable? A:Yes Q:How many devices can I hook up to a USB device? A:127