Hardware, Wake-up Process,
Boot-Up, Operating System
Control of Hardware
Dr. Harold D. Camp
IT 212 002
1 February 2007
Personal Computer Hardware
A typical pc consists of a case or chassis in desktop or tower shape and the following parts:
Motherboard or system board with slots for expansion cards and holding parts ** Central processing
Computer fan - used to cool down the CPU
Random Access Memory (RAM) - for program execution and short term data storage, so the
computer does not have to take the time to access the hard drive to find the file(s) it requires.
More RAM will normally contribute to a faster PC. RAM is almost always removable as it sits in
slots in the motherboard, attached with small clips. The RAM slots are normally located next to
the CPU socket.
Basic Input-Output System (BIOS) or Extensible Firmware Interface (EFI) in some newer computers
• CSI (expected in 2008)
• AGP (being phased out)
• VLB (outdated)
• ISA (outdated)
• EISA (outdated)
Personal Computer Hardware
Power supply - a case that holds a transformer, voltage control, and (usually) a cooling fan
Storage controllers of IDE, SATA, SCSI or other type, that control hard disk, floppy disk, CD-ROM
and other drives; the controllers sit directly on the motherboard (on-board) or on expansion cards
Video display controller that produces the output for the computer display. This will either be built into
the motherboard or attached in its own separate slot (PCI, PCI-E or AGP), requiring a Graphics
Computer bus controllers (parallel, serial, USB, FireWire) to connect the computer to external
peripheral devices such as printers or scanners
Some type of a removable media writer:
• CD - the most common type of removable media, cheap but fragile.
– CD-ROM Drive
– CD Writer
– DVD-ROM Drive
– DVD Writer
– DVD-RAM Drive
• Floppy disk
• Zip drive
• USB flash drive AKA a Pen Drive
• Tape drive - mainly for backup and long-term storage
Personal Computer Hardware
Internal storage - keeps data inside the computer for later use.
• Hard disk - for medium-term storage of data.
• Disk array controller
Sound card - translates signals from the system board into analog voltage
levels, and has terminals to plug in speakers.
Networking - to connect the computer to the Internet and/or other computers
• Modem - for dial-up connections
• Network card - for DSL/Cable internet, and/or connecting to other
In addition, hardware can include external components of a computer system.
The following are either standard or very common.
Personal Computer Hardware
Input or Input devices
• Text input devices
• Pointing devices
• Gaming devices
– Game controller
• Image, Video input devices
– Image scanner
• Audio input devices
Output or Output devices
• Image, Video output devices
– Printer Peripheral device that produces a hard copy. (Inkjet, Laser)
– Monitor Device that takes signals and displays them. (CRT, LCD)
• Audio output devices
– Speakers A device that converts analog audio signals into the equivalent air vibrations
in order to make audible sound.
– Headset A device similar in functionality to that of a regular telephone handset but is
worn on the head to keep the hands free.
A typical computer is built with the microprocessor, main memory, and other
basic components on the motherboard. Other components of the computer
such as external storage, control circuits for video display and sound, and
peripheral devices are typically attached to the motherboard via ribbon
cables, other cables, and power connectors.
A typical motherboard provides attachment points for one or more of the
following: CPU, graphics card, sound card, hard disk controller, memory
(RAM), and external peripheral devices. The connectors for external
peripherals are nearly always color coded according to the PC 99
Power supplies, often referred to as "switching power supplies", use switcher
technology to convert the AC input to lower DC voltages. The typical voltages
The 3.3- and 5-volts are typically used by digital circuits, while the 12-volt is used to
run motors in disk drives and fans.
Cases usually come with room for a power supply unit, several expansion slots and expansion bays, wires for
powering up a computer and some with built in I/O ports that must be connected to a motherboard.
Motherboards are screwed to the bottom or the side of the case, its I/O ports being exposed on the back of the
case. Usually the power supply unit is at the top of the case attached with several screws. The typical case has
four 5.25" and three 3.5" expansion bays for devices such as hard drives, floppy disk drives and CD-ROMs. A
power button and sometimes a reset button are usually located on the front. LED status lights for power and
hard drive activity are often located near the power button and are powered from wires that are connected with
the motherboard. Some cases come with status monitoring equipment such as case temperature or processor
# Capacity, usually quoted in gigabytes. (older
hard disks used to quote their smaller
capacities in megabytes)
# Physical size, usually quoted in inches:
* Almost all hard disks today are of either the
3.5" or 2.5" varieties, used in desktops and
DVD (commonly "Digital Versatile Disc"
or "Digital Video Disc") is an optical disc
storage media format that can be used
for data storage, including movies with
high video and sound quality. DVDs
resemble compact discs as their
diameter is the same (120 mm (4.72
inches) or occasionally 80 mm (3.15
inches) in diameter), but they are
encoded in a different format and at a
much higher density.
Instead of allowing random-access to data as hard disk drives do, tape
drives only allow for sequential-access of data. A hard disk drive can
move its read/write heads to any random part of the disk platters in a
very short amount of time, but a tape drive must spend a considerable
amount of time winding tape between reels to read any one particular
piece of data. As a result, tape drives have very slow average seek
times. Despite the slow seek time, tapes drives can stream data to
tape very quickly. For example, modern LTO drives can reach
continuous data transfer rates of up to 80 MB/s, which is as fast as
most 10,000 rpm hard disks.
The disk format itself had no more capacity than the more
popular (and cheaper) 5¼-inch floppies. Each side of a
double-density disk held 180 KB for a total of 360 KB per
disk, and 720 KB for quad-density disks. Unlike 5¼-
inch or 3½-inch disks, the 3-inch disks were designed to
be reversible and sported two independent write-protect
switches. It was also more reliable thanks to its hard
USB Flash Drives currently are sold from 32 megabytes up
to 64 gigabytes
Built into the motherboard, two connections
provide for ribbon cables that send signals
controlling disk drives
AGP Expansion Slots
The Accelerated Graphics Port (also called Advanced Graphics
Port) is a high-speed point-to-point channel for attaching a graphics
card to a computer's motherboard, primarily to assist in the
acceleration of 3D computer graphics. Some motherboards have
been built with multiple independent AGP slots. AGP is currently
being phased out in favor of PCI Express.
Width: 32 bits
Speed: up to 2133 MB/s
PCI Expansion Slot
The Peripheral Component Interconnect, or PCI Standard (in
practice almost always shortened to PCI) specifies a computer bus
for attaching peripheral devices to a computer motherboard. These
devices can take any one of the following forms:
An integrated circuit fitted onto the motherboard itself, called a planar
device in the PCI specification.
An expansion card that fits in sockets.
A video card, (also referred to as a graphics accelerator
card, display adapter and numerous other terms), is an
item of personal computer hardware whose function is
to generate and output images to a display. The term is
usually used to refer to a separate, dedicated expansion
card that is plugged into a slot on the computer's
motherboard, as opposed to a graphics controller
integrated into the motherboard chipset.
A sound card is a computer
expansion card that can input and
output sound under control of
computer programs. Typical uses
of sound cards include providing
the audio component for
multimedia applications such as
music composition, editing video
or audio, presentation/education,
and entertainment (games). Many
computers have sound
capabilities built in, while others
require these expansion cards if
audio capability is desired.
Random Access Memory (RAM)
Random access memory (usually known by its acronym,
RAM) is a type of data store used in computers. It takes
the form of integrated circuits that allow the stored data
to be accessed in any order — that is, at random and
without the physical movement of the storage medium
or a physical reading head.
The word "random" refers to the fact that any piece of data
can be returned quickly, and in a constant time,
regardless of its physical location and whether or not it
is related to the previous piece of data. This contrasts
with storage mechanisms such as tapes, magnetic disks
and optical disks, which rely on the physical movement
of the recording medium or a reading head. In these
devices, the movement takes longer than the data
transfer, and the retrieval time varies depending on the
physical location of the next item.
In electronics and especially synchronous digital circuits, a
clock signal is a signal used to coordinate the actions of two
or more circuits.
A clock signal oscillates between a high and a low state,
normally with a 50% duty cycle, and is usually a square
Circuits using the clock signal for synchronization may become
active at either the rising or falling edge, or both of the clock
Most integrated circuits (ICs) of sufficient complexity utilize a
clock signal in order to synchronize different parts of the
circuit and to account for propagation delays.
As ICs become more complex, the problem of supplying
accurate and synchronized clocks to all the circuits becomes
increasingly difficult. The preeminent example of such
complex chips is the microprocessor, the central component
of modern computers.
Basic Input/Output System
BIOS, in computing, stands for Basic Input/Output System also
incorrectly known as Basic Integrated Operating System. BIOS
refers to the firmware code run by a computer when first powered
on. The primary function of the BIOS is to prepare the machine so
other software programs stored on various media (such as hard
drives, floppies, and CDs) can load, execute, and assume control of
the computer. This process is known as booting up.
BIOS can also be said to be a coded program embedded on a chip
that recognises and controls various devices that make up the
computer. The term BIOS is specific to personal computer vendors.
Among other classes of computers, the generic terms boot monitor,
boot loader or boot ROM are commonly used.
A microprocessor (sometimes abbreviated µP)
is a programmable digital electronic
component that incorporates the functions of
a central processing unit (CPU) on a single
semiconducting integrated circuit (IC). The
microprocessor was born by reducing the
word size of the CPU from 32 bits to 4 bits, so
that the transistors of its logic circuits would fit
onto a single part. One or more
microprocessors typically serve as the CPU in
a computer system, embedded system, or
Heat Sink and Fan
A heat sink is an environment
or object that absorbs and
dissipates heat from another
object using thermal contact
(in either direct or radiant
Universal Serial Bus (USB)
Universal Serial Bus (USB) is a serial bus
standard to interface devices. It was originally
designed for computers, but its popularity has
prompted it to also become commonplace on
video game consoles, PDAs, portable DVD
and media players, cellphones; and even
devices such as televisions, home stereo
equipment (e.g., digital audio players), car
stereos and portable memory devices.
The radio spectrum based USB implementation is
known as Wireless USB.
A computer keyboard is a peripheral partially
modeled after the typewriter keyboard.
Keyboards are designed for the input of text and
characters and also to control the operation of a
An electrical connector is a device for joining electrical
circuits together. The connection may be temporary, as
for portable equipment, or may require a tool for
assembly and removal, or may be a permanent
electrical joint between two wires or devices. There are
hundreds of types of electrical connectors. In computing,
an electrical connector can also be known as a physical
A parallel port is a type of socket found on personal computers for
interfacing with various peripherals. It is also known as a printer
port or Centronics] port. The IEEE 1284 standard defines the bi-
directional version of the port.
For the most part, the USB interface has replaced the Centronics-style
parallel port — as of 2006, most modern printers are connected
through a USB connection, and often don't even have a parallel
port connection. On many modern computers, the parallel port is
omitted for cost savings, and is considered to be a legacy port. In
laptops, access to a parallel port is still commonly available through
In computing, a serial port is a serial communication physical interface through which
information transfers in or out one bit at a time (contrast parallel port). Throughout
most of the history of personal computers, data transfer through serial ports
connected the computer to devices such as terminals or modems. Mice, keyboards,
and other peripheral devices also connected in this way.
While such interfaces as Ethernet, FireWire, and USB all send data as a serial stream,
the term "serial port" usually identifies hardware more or less compliant to the RS-
232 standard, intended to interface with a modem or with a similar communication
For the most part, the USB interface has replaced the serial port — as of 2006, most
modern computers are connected to devices through a USB connection, and often
don't even have a serial port connection. The serial port is omitted for cost savings,
and is considered to be a legacy port.
A modem (from modulate and demodulate) is a
device that modulates an analog carrier
signal to encode digital information, and also
demodulates such a carrier signal to decode
the transmitted information. The goal is to
produce a signal that can be transmitted
easily and decoded to reproduce the original
Faster modems are used by Internet users every
day, notably cable modems and ADSL
An operating system (OS) is a computer program that
manages the hardware and software resources of a
computer. At the foundation of all system software, the
OS performs basic tasks such as controlling and
allocating memory, prioritizing system requests,
controlling input and output devices, facilitating
networking, and managing files. It also may provide a
graphical user interface for higher level functions. It
forms a platform for other software.
• Process Management
• Disk and File Management
• Internal/External Security
• Graphical User Interfaces (GUI)
• Device Drivers
Microsoft Windows OS
The Microsoft Windows family of operating systems originated as a graphical layer on
top of the older MS-DOS environment for the IBM PC. Modern versions are based
on the newer Windows NT core that first took shape in OS/2 and borrowed from
VMS. Windows runs on 32-bit and 64-bit Intel and AMD processors, although earlier
versions also ran on the DEC Alpha, MIPS, Fairchild (later Intergraph) Clipper and
PowerPC architectures (some work was done to port it to the SPARC architecture).
As of 2006, Windows held a near-monopoly of around 94% of the worldwide desktop
market share, although some predict this to dwindle due to the increased interest in
open source operating systems. It is also used on low-end and mid-range servers,
supporting applications such as web servers and database servers. In recent years,
Microsoft has spent significant marketing and R&D money to demonstrate that
Windows is capable of running any enterprise application which has resulted in
consistent price/performance records (see the TPC) and significant acceptance in
the enterprise market at the cost of existing Unix based system market share.
Other Operating Systems
Macintosh Operating System
Apple deliberately downplayed the existence of the operating system in the early years of the
Macintosh to help make the machine appear more user-friendly and to distance it from other
operating systems such as MS-DOS, which were portrayed as arcane and technically
challenging. Apple wanted Macintosh to be portrayed as a computer "for the rest of us". The term
"Mac OS" did not really exist until it was officially used during the mid-1990s. The term has since
been applied to all versions of the Mac system software as a handy way to refer to it when
discussing it in context with other operating systems.
Unix systems run on a wide variety of machine architectures. They are used heavily as server
systems in business, as well as workstations in academic and engineering environments. Free
software Unix variants, such as Linux and BSD, are popular but have not reached significant
market share in the desktop market. They are used in the desktop market as well, for example
Ubuntu, but mostly by hobbyists.
How a Disk Boot Wakes Up a PC
• A personal computer can't do anything useful unless it's running an
• A basic type of software, such as Microsoft Windows, that acts as a
supervisor for all the applications, games, or other programs you use.
• The operating system sets the rules for using memory, drives, and
other parts of the computer.
• Before a PC can run an operating system, it needs some way to
load the operating system from disk to random access memory
• The way to do this is with the bootstrap, or simply to boot—a small
amount of code that's a permanent part of the PC.
Power On Self Test
• Turn on your PC, electricity warms up the components that send, receive, and memorize bits and bytes
of data rushing through the system. One stream of electricity follows the same permanently programmed
path it has followed each time the computer came to life.
• The path takes current to the CPU, or microprocessor. The electrical signal clears leftover data from the
chip's internal memory registers and places a specific hexadecimal number, F000, into one of the CPU's
digital note pads, called the program counter.
• Whatever number is in the program counter tells the CPU the memory address of the next instruction. In
this case, it's the first instruction, located on a flash memory chip on the computer's motherboard. This
chip holds a few small programsthat determine how your computer works. All together, they're called the
• Now the BIOS awakens the computer's components, performing the power-on self-test (POST) to make
sure the computer is functioning properly.
• BIOS checks a small, 64-byte chuck of RAM that is kept alive by a battery even when the
computer is off that contains the official record of which components are installed in your system.
• The BIOS and CPU check to make sure they're working right.
• The BIOS loads device drivers and interrupt handlers into memory the for the basic hardware in
the system, such as the keyboard, mouse, hard drive, and floppy drive.
• To be sure all the PC's operations function in a synchronized, orderly fashion, the CPU also
checks the system's clock, which is responsible for pacing signals.
• The CPU sends signals over the system bus to be sure all of the components are functioning.
• The POST tests the memory contained on the display adapter and the video signals that control
the display. At this point, you'll first see something appear on your PC's monitor.
• The BIOS checks to see if it's engaged in a cold boot, meaning the computer had been turned
off, or if it's a warm boot, or reboot, by checking the value at memory address 0000:0472.
• For a cold boot the BIOS runs a series of tests to ensure that the RAM chips are functioning
• The tests write data to each chip, and then read it and compare what they read with the
• The POST sends signals over specific paths on the bus to the internal floppy, optical, and
hard disk drives, and listens for a response to determine which drives are available.
After the POST
• A typical Windows XP boot sequence starts
with the MBR loading the bootstrap loader for
the OS, which will tell the computer
everything it needs to know about its memory
and how to use it, how the files are stored,
and put up the boot menu.
• In many computers, the boot menu is not
shown unless the user asks for it. The
bootloader then launches a program that
collects more information about the hardware
installed in it and then loads the core
operating system files.
• Then, it reads the registry from which it
gathers the information necessary to
communicate with different components, and
then load the necessary programs (drivers)
to communicate with devices attached to the
After the POST
Once this is done, the bootloader loads the program that
shows the welcome or logon screen. Once the user logs
in, the computer loads the shell (Explorer), which shows
the desktop to the user. At this point, the OS is loaded
and the computer is ready for use.
A typical boot takes about a minute, with the BIOS boot
sequence taking about 10-15 seconds.
The term booting is short for bootstrapping. The word
bootstrapping is derived from the phrase "pulling himself
up by his bootstraps", which has its origins in the tall
stories narrated by Baron Munchhausen, a German
nobleman in the eighteenth century.
How an Operating System Controls PC
originally were developed
to handle one of the most
communicating with a
variety of disk drives. This
is evidenced by the names
given to early operating
systems, which often
contained the acronym
DOS, for disk operating
system. Eventually, the
operating system quickly
evolved into an all-
between your PC and the
software you run on it.
How Hardware and Software Work
• Choose a command, like save
• Word processor tells OS to save
• OS knows how to control hardware
• OS does infrastructure work
• Program does your work
How Hardware and Software Work
• A device driver, or a software driver is a specific type of computer
software, typically developed to allow interaction with hardware devices.
• This usually constitutes an interface for communicating with the device, through
the specific computer bus or communications subsystem that the hardware is
• Driver provides commands to and receives data from the device, and on the
other end, the requisite interfaces to the operating system and software
• Often called simply a driver, it is a specialized hardware-dependent
computer program, which is operating system specific, that enables
another program, typically an operating system or applications software
package, to interact transparently with the given device.
• Usually provides the requisite interrupt handling required for any necessary
asynchronous time-dependent hardware interfacing needs.
Types of Hardware Drivers
Because of the diversity of modern hardware and operating systems, many ways exist in
which drivers can be used. Drivers are used for interfacing with:
• Video adapters
• Network cards
• Sound cards
• Local buses of various sorts - in particular, for bus mastering on modern systems
• Low-bandwidth I/O buses of various sorts (for pointing devices such as mice,
keyboards, USB, etc.)
• computer storage devices such as hard disk, CD-ROM and floppy disk buses (ATA,
• Implementing support for different file systems
• Implementing support for image scanners and digital cameras
Enhanced Integrated Drive Electronics
• A disk drive device driver
• An enhanced version of the IDE drive interface
• Expands the maximum disk size from 504 MB to 8.4
• More than doubles the maximum data transfer rate,
• And supports up to four drives per PC (as opposed to
two in IDE systems).
• Now that hard disks with capacities of 1 GB or
more are commonplace in PCs,
• EIDE is an extremely popular interface.
• EIDE's primary competitor is SCSI-2, which also
supports large hard disks and high transfer rates.
Enabling Disk Access
• Disk controller translates instructions from
the BIOS and Disk Drivers into electrical
• Move drive’s read/write head to proper
• Create or read magnetic signals that
1. Press a key, an electrical signal identifies what key you pressed, to
the keyboard controller.
2. The keyboard interrupt arrives on one of 16 interrupt request (IRQ)
lines. Seven of the IRQs monitor specific components, such as the
3. The controller relays a signal to the interrupt controller that determines
which of the 256 possible kinds of interrupts request the CPU's
4. More than one expansion card on the PCI Peripheral Component
Interconnect (PCI) and PCI-Express slots can use the same IRQ
because the requests are managed by the Plug 'n' Play function.
5. The interrupt controller sends a signal called the INTR, used for
normal interrupt signals.
6. The CPU puts whatever it was doing on hold.
7. A CPU uses one of two methods from computing: polling and
8. The CPU checks to find out what key you pressed. The CPU checks a
section of memory called the interrupt descriptor table (IDT).
Specifically, the CPU performs the instructions at one of the IDT's
locations associated with the key.
9. When the interrupt software completes its job, it sends an instruction
to the CPU. That tells the CPU it is free to return to whatever it was
doing before it was interrupted.
How Plug and Plan Works
With Plug and Play under Microsoft Windows Server 2003, you can connect a hardware
device to your system and leave the job of configuring and starting the device to the
operating system. If the device and drivers are not designed to take advantage of
Plug and Play, Windows Server 2003 will not be able to automatically configure and
start the device. Plug and Play in Windows Server 2003 supports a wide range of
In Windows Server 2003, Plug and Play support is optimized for computers that include
an Advanced Configuration and Power Interface (ACPI) BIOS. ACPI devices are
defined by the Advanced Configuration and Power Interface (ACPI) Specification, a
hardware and software interface specification that combines and enhances the Plug
and Play and Advanced Power Management (APM) standards. ACPI devices
include low-level system devices such as batteries and thermal zones.
Plug and Play detection runs with the logon process and relies on system firmware,
hardware, device drivers, and operating system features to detect and enumerate
new devices. ACPI firmware provides enhanced features, such as hardware
resource sharing. When Plug and Play components are coordinated,
Windows Server 2003 can detect new devices, allocate system resources, and
install or request drivers with minimal user intervention.
Plug and Play Architecture
Plug and Plan Driver Installation
When a hardware device is connected — as when
you plug a USB camera into a USB port — Plug
and Play Manager goes through the following steps
to install the device.
• After receiving an insertion interrupt, Plug and Play
Manager checks what hardware resources the
• memory ranges, I/O ranges, and DMA
channels. Plug and Play Manager then assigns
• Plug and Play Manager checks the hardware
identification number of the device.
• Plug and Play Manager then checks the hard drive,
floppy drives, CD-ROM drives, and Windows
Update for drivers that match the number of the
• If multiple drivers are found, Plug and Play
Manager chooses the driver that is the best match
by looking for the closest hardware ID or
compatible ID match, driver signatures, and other
• Plug and Play Manager then installs the best-match
driver and the operating system starts the device.
Prepare a single page paper addressing each
of the following questions:
• What is the registry?
• What does it do?
Due Next Week
• How does it work?
• Why does a PC require a registry?