Transcript Overview of computer hardware

Basic Hardware Overview
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System Case
• The major hardware components of the computer,
as opposed to the I/O devices and other
peripherals, are housed in the case.
– Also known as chassis or enclosure or system unit.
• The case helps keep the components clean and
cool.
• It can also provide some shielding to undesired
outside voltages.
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Case with
side panel
removed.
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More than just a box
• At first the case strikes one simply as a container,
but it has some structure.
• If one is building a PC, the case has to be
coordinated with the motherboard one chooses.
• The case will also determine how much access
there is to the front and back of the PC – the
number of bays, expansion slots and so on.
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• Cases come is various sizes and shapes,
known as “form factors”
– Micro tower, mini tower, mid tower, full tower,
microATX desktop, and ATX desktop.
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Power Supply
• Computers work by having a value – in binary
computers a high or low – represented by some
physical quantity.
• The physical quantity is typically an electronic
voltage or electronic current.
• Thus we need some part of the computer
responsible for supplying electronic voltages
and/or currents. This is the power supply.
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Power Supply is really a transformer
• As far as the other parts of the computer are concerned the
power does come from the power supply – except for a
few parts that have a separate battery.
• However, strictly speaking the device known as a power
supply does not supply power, it transforms it. The source
of the power is a generating station, the power is then
delivered to buildings and made available at wall outlets.
The power supplied by the outlet must be transformed into
the form that is useful for computers.
– One could also complicate the scenario with an Uninterruptible
Power Supply (UPS) or a back-up generator.
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AC-DC
• The outlet supplies somewhat high-voltage AC
(alternating current)
– In the US, the AC supplied is known as 110, it varies
from approximately a positive 156 volts to a negative
156 volts many times a second.
• Computers need low-voltage DC (direct current)
– Various components need differing amounts of steady
voltage (12 volts, 5 volts, ±3.3 volts, etc.)
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Caution
• Because of the relatively high voltages
coming in and the way in which
transformation is done, power supplies can
be dangerous.
• Do not open up a power supply, unless you
have been trained.
• Usually if a power supply goes, it is
replaced as a unit.
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Power to the components
• The transformed power must in turn reach the
components that use it:
– The motherboard and the devices thereon
– The various drives (floppy, hard disk, CD)
– Etc.
• There is a special (larger) connector to the mother
board.
• The drives are connected with the smaller Molex
connectors and the even smaller Mini connectors.
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Parts of a Power Supply
Molex Connector
Mini
Connector
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Motherboard
• A circuit is a path or paths which current through a set of
electronic components (resistors, capacitors, transistors,
etc.).
• If a number of the components are etched into a
semiconductor, this is called a chip or integrated circuit.
• If a circuit or circuits are printed onto a board, this is called
a circuit board.
– Sometimes one inserts chips into boards.
• The main circuit board is a computer is known as the
motherboard.
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The place to meet
• The major components are on the motherboard or
plug into it.
• The motherboard has places for processor, cache
and memory to plug into.
• These components interface with other
components via the chipset.
• The chipset leads to the controllers of various
other components (floppy drive, hard drive,
keyboard, mouse, etc) and to expansion slots so
that other circuitry can be added making the PC
customizable.
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Chipset
• Most of the manipulation of data is done by the
processor. The rest is mostly moving data around.
And the main traffic cop is the chipset.
• The chipset allows the storage and input devices to
interface with the processor, memory and cache.
• The chipset will determine which processors can
be used in the PC, how much cache and memory
are allowed, etc.
• Since the chipset interfaces the components with
vastly different speeds, it can be crucial is
determining a PC’s performance.
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Controllers
• Whereas the chipset is a centralized, generic
data-flow manager; controllers are
individual, specific data-flow managers
that allow one to interface with specific
devices.
• Hence one has a floppy controller, a
keyboard controller, and so on.
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Buses
• If the motherboard’s chipset and controllers are the
traffic cops, then the motherboard’s buses are the
streets.
• Since so many devices want to interface with the
processor, there is a set of shared channels for
information going to or coming from the processor.
These are the buses.
• Like streets, they can vary in speed and capacity.
There are fast buses for fast devices and slow buses
for slow devices.
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BIOS
• The Basis Input/Output System or BIOS is
firmware (instructions burned into ROM)
that interface between the various hardware
components on and plugged into the
motherboard and the operating system.
• This layering means that the operating
system is not dependent the specifics of the
hardware.
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BIOS
• The BIOS is written in ROM because it rarely
changes. It may be in EEPROM (Electrically
Erasable Programmable Read-Only Memory) so
that it can be changed occasionally – flashing the
BIOS.
• Being ROM also implies that these instructions
are non-volatile – not lost when the power goes
off. Thus the instructions for starting the PC are
written in this way.
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Processor
• The processor, a.k.a. the Central Processing Unit
or CPU interprets the instructions it finds in
memory (programs) and responds to and modifies
(i.e. processes) the information and directs the
other components how to respond.
• The CPU is sometimes thought of as consisting of
two parts:
– The Arithmetic Logic Unit (ALU)
– Control
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Pentium 4
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Processor
• The processor is the most important chip in a PC –
often called the brain of the computer.
• The processor has a lot of contacts called pins
which plug into the motherboard and allow
electronic information to flow to and from the
processor.
• The pins are arranged in rows around the chip’s
perimeter in what is known as the Pin Grid Array
PGA.
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Processor features
• Two of the main features of processors are their
speed and their instruction set.
• Instructions are broken down into their smallest
steps and the processor speed determines the
amount of time required for one of these smallest
steps.
• A processor’s instruction set is the collection of
basic things it knows how to do.
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System Memory
• The processor executes instructions. The
combination of instructions can be varied – that is
computers can be programmed.
• The combination of instructions as well as the data
that the processor is currently acting on are held in
memory.
• Memory can be distinguished from storage by its
intimate connection to the processor and by its
volatility – data in memory, Random-Access
Memory (RAM) is lost when the power goes off.
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Cache
• There are two basic types of RAM
– Static RAM (SRAM) is fast but expensive
– Dynamic RAM (DRAM) is slow but cheap
• The processor’s speed is faster than main memory
which is made of DRAM. A special unit of faster
SRAM memory works even more intimately with
the processor than memory is known as cache.
• Cache is a very sophisticated game of guessing
what instructions and data the processor will next
need and placing it in the location that can be
accessed more efficiently.
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Storage
• Memory is essential (otherwise computers would
not be programmable), storage is simply a
convenience and was not a part of the earliest
computers.
• But without storage the programs and
accompanying data would have to be entered
anew each time.
• Storage is nonvolatile (keeps the information)
without needing power – so that programs and
data can be kept from execution to execution, day
to day, year to year.
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Hard disk drive
• The main storage device is the hard disk.
• The hard disk uses a magnetic material.
The magnetic property can be placed in two
states corresponding to 1’s and 0’s.
• The magnetic state can be determined
(read) or set (written) by electronic means
but the state can be maintained without
constant electric power.
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Floppy Disk Drive
• Hard drives are usually permanent within the case,
a storage medium that can be taken out of the case
is said to be removable. (Some hard drives are
removable.)
• The earliest storage in PCs was a removable
magnetic medium known as the floppy disk.
• Early on, floppy disks shrunk in size and gained in
capacity but this stopped at 3-1/2 inch floppy disk
with 1.44 MB of storage that is standard today.
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CD ROM Drive
• CDs (Compact Disks) are an optical medium of
storage that has become standard in PCs.
• A standard CD has about a thousand times the
capacity of a floppy disk.
• Originally CDs were Read Only (CD-ROM), written
by the manufacturer and useful as a software delivery
system.
• As the amount of data users wanted to be portable
grew, a recordable CD (CD-R) filled the void. But it
had the limitation of being Write Once. Finally the
rewritable CDs (CD-RW) became available.
• DVDs are similar to CDs but have higher capacity.
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Keyboard
• Early computers inputting was done by plugging
wires in boards or flipping switches or paper tape
or punch cards. But the keyboard made data entry
user friendly.
• PCs have always had generic connectors to plug in
devices so that users could adapt them to various
purposes, but the keyboard is so standard it soon
had a designated connector and controller on the
motherboard.
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Mouse
• The mouse was not a standard input device in early PCs.
(They were initially frowned upon by people who
considered themselves serious computer users.)
• But the user friendly graphical user interface (GUI)
approach made using a computer more palatable to most
users and it soon became standard with its own designated
connector.
• The trend for devices becoming standard and having
designated connectors has changed somewhat recently
with the introduction of the USB (universal serial bus) and
USB keyboards and USB mice.
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Displays
• The earliest display devices were lights or
light-emitting diodes (LEDs). However,
any significant amount of binary output is
difficult to read.
• The monitor was an early standard output
device. Early monitors were monochrome
Cathode Ray Tubes (CRTs) – the same
basic technology as television.
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CRTs
• A stream of electrons (a cathode ray) is aimed
toward the screen which is coated with various
phosphors; the electrons transfer their energy to
the phosphors which then glow.
• There are phosphors for red and green and blue
which can be combined to make all other colors.
• An individual speck is known as a pixel and the
number of pixels determines the screen’s
resolution.
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LCDs
• CRT’s are OK for desktop computers, but laptops
require something smaller and lighter; they need
“flat panel displays.”
• The most common flat panel display is the liquidcrystal display (LCD).
• Liquid crystals are molecules said to be in a state
between liquid and solid.
• Their optical properties are affected by electric
current or fields, hence their use as displays:
watches, laptop screens, etc.
• Flat panels are replacing CRTs even on the desktop.
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Expansion Cards
• The video card – extra circuitry needed to
interface with the monitor – added to the
capability of PCs.
• In order to make PCs customizable, they
have expansion slots – places where extra
circuit boards called expansion cards can be
added.
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NIC
• PCs were initially stand-alone devices. But
networking proved to be important and then
crucial. The PC’s expansion slots allowed a
user to add a Network Interface Card (NIC)
to allow the computer to exchange
information with other computers.
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Ports
• In addition to expansion slots which allowed one
to add circuitry to interface with peripherals, PCs
also had two standard interface paradigms that if a
device could use these, additional circuitry was
not needed. The device could just be plugged in.
• These places to plug theses devices are called
ports and the two standards developed are serial
connection and parallel connection.
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Serial Communication
• A serial connection sends information over
the line one bit at a time. It is a simple way
to send information in or out of the
computer, but is not as fast as other ways
the computer can communicate. Serial
connections are typically used for devices
such as mice and modems.
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DB Connector
• While serial data flows one bit at a time and
can flow along a single wire. There’s more
to communication than just flow of
information. The two devices must agree to
communication, so there are additional
wires needed.
• A generic serial connector is the DB
connector. (DB – databus)
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Parallel Communication
• A parallel connection sends many bits in parallel.
The advantage of this is that it is faster, but the
disadvantage is that it is more complicated to do.
Parallel connections are used most often for printers
and removable storage drives, which need more
speed than serial peripherals.
• Recently advances in serial connections have made
them competitive with parallel connections. And
devices such as printers conventionally thought of
as strictly parallel devices are no longer thus.
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References
•
•
•
•
http://www.pcguide.com/
http://www.webopedia.com
http://www.whatis.com
PC Hardware in a Nutshell, Thompson and
Thompson
• A+ Certification: Exam Guide, Meyers and
Jernigan
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