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Version 3.1
Hardware Basics
How Computers Work
Version 3.1 2
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.
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Bootstrap
• For an operating system to run, it must be loaded into the
Random Access Memory (RAM)of the computer.
• When a computer is first turned on, it launches a small
program called the bootstrap loader that is built into the
hardware of the computer.
• Specifically, the bootstrap is located on the BIOS chip, which
resides on the system board.
• The primary functions of the bootstrap are to test the
computer hardware and to locate and load the operating
system into RAM.
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Power-On Self Test
• To test the computer hardware, the bootstrap program runs a
program called power-on self-test or POST. In this test, the Central
Processing Unit (CPU) checks itself first and then checks the
computer 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.
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Loading the Operating System
• The next step for the bootstrap program is to locate the OS
and copy it to the computer RAM.
• When the bootstrap finds the OS boot record, it is copied to
the computer RAM and the bootstrap program turns over the
control of the boot process to the boot record.
• As files are located and loaded into RAM, the boot record is
no longer needed. The OS that was stored on the hard disk is
now in control of the boot process.
Version 3.1 6
Motherboards
• also called the system board or main board.
• is the data and power infrastructure for the entire computer.
• 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.
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The major components on the motherboard include the chipset, CPU socket, expansion sockets, I/O support, BIOS, RAM sockets, power supply socket, CMOS chip, dipswitches and jumpers, and the memory cache.
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Motherboard Form Factors• Motherboards are usually described by their form factors,
which describe their physical dimensions. The two most
common form factors in use today are the Baby AT
motherboard and the ATX motherboard.
• 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.
Version 3.1 10
Central Processing Unit
• On the motherboard, the CPU is contained on a single
integrated circuit called the microprocessor.
• CPU Terminologies⁻ Bus is responsible for delivering data from one location on the
PC to another. ⁻ Data bus is the term used to define the pathway between the
processor and memory.•32 bit processor means 32 bit of info at a clock cycle•64 bit processor means 64 bit of info at a clock cycle
-Address bus dictates how much physical memory the processor can access.
Newer processors have 36-bit address buses, 68,719,476,736 memory addresses, or 64GB of memory access is possible.
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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. It is typically expressed in megahertz (MHz),
and the higher the number, the faster the processor.
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•There are two types of cache memory for the CPU: L1 (Level 1) cache is built into the processorL2 (Level 2) cache resides outside the processor. In the past, L2 cache resided on the motherboard, but newer processors have a bit of L1 and L2 cache in the chip package.
•The more cache memory a processor has, the quicker (and more expensive) the system will be.•A dual core processor combines two independent processors and the L1 cache from those processors onto a single processor chip. The benefit of a dual core processor is that it can execute multiple threads at the same time without hyperthreading because you essentially have two processors.•Hyperthreading technology, or HTT, allows a processor to logically act as two different processors by being able to execute simultaneous threads.
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CPUSocket Type AMD Intel
Socket 8
Pentium Pro 150-200 MHz, Pentium II Overide 300-333 MHz
Slot 1
Celeron, Pentium II 233-450 MHz, Pentium III 450 MHz
Slot 2
Pentium II Xeon 400-450 MHz, Pentium III Xeon 500-1 GHz
Slot A Athlon 500 MHz - 1 GHz
Socket 370
Celeron, Pentium II 233-450 MHz, Pentium III 450 MHz - 1.13 GHz
Socket ADuron 600 MHz +, Athlon 750 MHz +
Socket 423 Pentium4 1.3 GHz +
Socket 603 Xeon 1 GHz - 1.4 h.z
Only used about 1 year.
Version 3.1 14
Expansion Slots
• Expansion slots, also known as sockets, are receptacles on
the computer motherboard that accept printed circuit boards.
• All computers have expansion slots that allow additional
devices to be added.
• Video cards, I/O cards, and sound cards are examples of
components that are located in expansion slots.
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Expansion Slots
• The common expansion slots that are likely to be encountered include the following:
• Industry Standard Architecture (ISA )
• Peripheral Component Interconnect (PCI )
• Accelerated Graphics Port (AGP)
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AGP Slot
• The Accelerated Graphics Port (AGP) was developed by Intel.
• AGP is a dedicated high-speed bus that is used to support the high demands of graphical software.
• This slot is reserved for video adapters.
• This is the standard graphics port in all new systems.
Version 3.1 17
PCI Slot
• The Peripheral Component Interconnect (PCI) is a 32-bit local bus slot developed by Intel.
• Since they talk to the motherboard at 33 MHz, the PCI bus slots offer a significant improvement over ISA or EISA expansion slots.
Version 3.1 18
Random Access Memory (RAM)
• RAM is considered temporary or volatile memory.
• The contents of RAM are lost when the computer power is turned off.
• RAM chips on the computer motherboard hold the data and programs that the microprocessor is processing.
• In other words, RAM is memory that stores frequently used data for rapid retrieval by the processor.
• RAM can be installed on the motherboard, either as a permanent fixture, or in the form of small chips, referred to as Single Inline Memory Modules (SIMMs – 72pins or 32bit data) or Dual Inline Memory Modules (DIMMs – 168pins or 64bit data).
Version 3.1 19
Classes of RAM
There are two classes of RAM that are commonly used today.
• Static RAM (SRAM)
• Dynamic RAM (DRAM).
Version 3.1 20
Static Ram (SRAM)
• SRAM is relatively more expensive, but it is fast and holds data when the power is turned off for a brief period of time.
• SRAM is used for cache memory.
• DRAM is inexpensive and somewhat slow.
• It requires an uninterrupted power supply to maintain the data.
• DRAM stores data in tiny capacitor that must be refreshed to maintain the data.
• Currently, Double Data Rate (DDR) is used as a RAM mostly. DDR memory gets its name from the fact that it can transfer data twice during each clock cycle. (200MHz -400MHz speed)
Dynamic Ram (DRAM)
Version 3.1 21
Monitors
• Computers are usually connected to a display, also called a
monitor.
• Some key monitor-related terms are: pixels, refresh rate,
resolution, and size.
– 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).
Version 3.1 22
Monitors
– Resolution – Varies based on the number of pixels. The more
pixels in the screen, the better the resolution. Better resolution
means a sharper image. The lowest screen resolution on
modern PCs is 640 x 480 pixels, which is called Video Graphics
Array (VGA). (This is the default resolution after installing a
video card using Windows.)
– Monitor screen sizes – Measured in inches. The most common
sizes are 14", 15", 17", 19", and 21" screens, measured
diagonally.
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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.
• There are different types of ports on the computer that serve
different purposes.
• An I/O port is a pathway into and out of the computer.
Version 3.1 24
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.
• Serial ports are sometimes called the RS-232 ports because they use the RS-232C standard as defined by the Electronics Industry Association (EIA).
• The DB-9 shown is a 9-pin male connector.
Version 3.1 25
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, LPT2, or LPT3.
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Parallel Ports
• PS/2 keyboard or PS/2 mouse ports are used to connect your
PC to its keyboard and mouse.
• Though both ports look identical, the mouse (green) and
keyboard (purple) ports are not interchangeable.
• Usually both ports are color coded or labeled to avoid any
confusion.
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Universal Serial Bus (USB)
• USB is an external port that allows the user to connect up to 127 external PC peripherals.
• External peripherals include the following: - USB keyboards- Mice - Printers - Modems - Scanners - Digital cameras - Digital video cameras - External disk drives
*USB devices can be hot-plugged.
Version 3.1 28
EIDE and SCSI Controllers
• The internal hard drive (discussed later in this module) is
connected to a disk controller with a 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.
Version 3.1 29
EIDE Controllers
• Enhanced IDE (EIDE) is the "new and improved" Integrated
Drive Electronics (IDE) drive interface.
NB The actual IDE controller is the circuitry located on the circuit
board on the drive itself — it is responsible for controlling the
flow of information to and from the drive.
Characteristic IDE EIDE Size 528MB 200GB and higher Devices in Chain 2 4 Transfer Rate 10 MBps 16 MBps and above Types of Devices Hard drives Hard drives, CD-ROMs
Version 3.1 30
SCSI Controllers
• The Small Computer Systems Interface (SCSI ) controller
• Like EIDE, SCSI devices have the controlling electronics on each of
the drives.
• A standard SCSI interface will allow up to seven devices 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.
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SCSI Controllers
• SCSI devices are typically connected in a series, forming a
chain that is commonly referred to as a daisy chain.
• The two SCSI devices at either end of the daisy chain must
be terminated.
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SATA -is a serial technology, it offers great speed (30 times faster) and other benefits over IDE drive controllers.•is with current speeds of 150 Mbps and future speeds of 600 Mbps.•is that it is a hot-swappable technology, meaning that you can add or remove drives from the system without shutting the system down. •its cables can be 39 inches long, while the maximum distance for IDE is 18 inches (gives you more flexibility).•uses only 7 wires, as opposed to the 80 wires used in newer IDE drives. The benefit here is that it allows for better airflow in the system, which results in a cooler system.If you don’t have a motherboard that has SATA connectors on it, then you can get a PCI card that does have the connectors.
The Serial ATA (SATA) Hype!
Version 3.1 33
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.
Version 3.1 34
Hard Disk Drive Components
• All hard disk drives share a common set of components.
These components include: 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.