Central Processing Unit
Part III
Bayram Güzer
Personal Computer Chips
• The chips in personal
computers is attached to
the motherboard.
• Flat main circuit board
that holds the computer
circuitry is called as
motherboard.
• Motherboard also holds
expansion slots into which
other circuit boards can be
inserted to link peripheral
devices to the processor.
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Personal Computer Chips
• Microprocessors is the
central processing unit
of the motherboards
which is the most
important component
of the motherboard.
3
Microprocessors
• A miniaturized central
processing unit can be
etched (fixed) on a chip,
made from a tiny square
of silicon.
• When it is used to
control specialized
devices (such as the fuel
system of a car) it is
called as a logic chip.
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Microprocessors
• Microprocessors
contains tens of millions
of tiny transistors.
• Microprocessors
contains three key
components;
– Control unit and
arithmetic logic unit
– Registers
– Clock
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Transistors
• Transistors are electronic switches that may or
may not allow electric current to pass through
– If current passes through, then the switch is on,
representing a 1 bit
– Otherwise, the switch is off, representing a 0 bit
– Thus combinations of transistors can stand for
combinations of bits, which as discussed earlier,
represents digits, letters and special characters.
6
Types of Chips
• There are lots of processor producing companies in the world
but market for the desktop computers and laptops are greatly
shared by Intel and AMD.
• Intel processors
– Price range from 100 TL to 3000 TL (source: hepsiburada.com, 24/10/2011)
– Common proccessor technology
• Sandy bridge, core i5, core 2 duo, core i7, celeron, pentium4 dual,
core i3, core 2 quad
– Socket technology
• 775 pin, 1155 pin, 1156 pin, 1366 pin.
• AMD processors
– Price range from 50 TL to 1000 TL (source: hepsiburada.com, 24/10/2011)
– Common proccessor technology
• Phenom, athlon II X4, Athlon 64 X2, Sempron, Athlon II X2,
Fusion, Athlon II X3.
– Socket technology
• Socket AM3, Socket FM1
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Memory Components
• Semiconductor Memory
• RAM and ROM
• Flash Memory
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Semiconductor Memory
• It is used by most modern computers which
is which is made up of thousands of very
small circuits that is pathways for electric
currents.
– Reliable, inexpensive, and compact
– Volatile: requires continuous electric current
• If the current is interrupted, data is lost
9
Semiconductor Memory
– Complementary Metal Oxide Semiconductor
(CMOS) is one of the important types of
semiconductor.
• It requires relatively little power.
• In PCs, CMOS is used in CMOS RAMs.
• Keeps information when power is shut down
– Since there is a special battery power.
• Used to store information needed when the
computer boots such as time, date and etc…
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RAM and ROM
• Random Access Memory (RAM)
• Read-Only Memory (ROM)
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Random Access Memory
• Data can be accessed
randomly
– Memory address 10
can be accessed as
quickly as memory
address 10,000,000
• Types:
– Static RAM (SRAM)
– Dynamic RAM
(DRAM)
• Packaged on circuit
boards
– Single in-line memory
modules (SIMMS)
– Dual in-line memory
modules (DIMMS)
12
Static RAM
• Retains its contents with intervention from
CPU
• Faster and more expensive than DRAM
• Typically used for Level 2 cache
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Dynamic RAM
• Must be continuously refreshed by CPU or
it loses its contents
• Used for personal computer memory
– Synchronous DRAM (SDRAM): faster type of
DRAM used today
– Rambus DRAM (RDRAM): faster and
expensive than SDRAM.
14
Read-Only Memory
• Contains programs and data permanently
recorded into memory at the factory
– Cannot be changed by user
– Not volatile: contents do not disappear when
power is lost
• Programmable ROM (PROM) chips
– Some instructions on chip can be changed
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Flash Memory
• Nonvolatile RAM
– Used in cellular phones, digital cameras, and
some handheld computers
– Flash memory chips resemble(like) credit cards
– Smaller than disk drive and require less power
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The System Bus
• Parallel electrical paths that transport data
between the CPU and memory
• Bus width
– The number of electrical paths to carry data
– Measured in bits
• Bus speed
– Measured in megahertz (MHz)
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Bus Width
• Typically the same as CPU’s word size
• With a larger bus size, CPU can:
– Transfer more data at a time
• Makes computer faster
– Reference larger memory address numbers
• Allows for more memory
– Support a greater number and variety of
instructions
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Bus Speed
• The faster the bus speed, the faster data
travels through the system
• Personal computers have bus speeds of 400
or 533 MHz
• ..\..\..\..\Documents and
Settings\Dersler\Desktop\microprocessors\HowStuffWorks Bus
Speed.webarchive
• ..\..\..\..\Documents and
Settings\Dersler\Desktop\microprocessors\Front-side bus - Wikipedia,
the free encyclopedia.webarchive
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Expansion Buses
• Adds peripheral devices to system
– Expansion boards
– Ports
– Common expansion buses
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Expansion Boards
• Connect to expansion
slots on motherboard
– Used to connect
peripheral devices
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Ports
• External connectors to plug in peripherals
such as printers
• Two types of ports
– Serial: transmit data one bit at a time
• Used for slow devices such as the mouse and
keyboard
– Parallel: transmit groups of bits together sideby-side
• Used for faster devices such as printers and
scanners
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Common Expansion Buses and Ports
• Industry Standard Architecture (ISA) bus
– Used for slow devices such as the mouse and modem
• Peripheral Component Interconnect (PCI) bus
– Used for faster devices such as hard disks
• Accelerated Graphics Port (AGP)
– Provides faster video performance
• Universal Serial Bus (USB) port
– Allows you to convert many devices in a series into the USB port
• IEEE 1394 bus
– A high-speed bus normally used to connect video equipment
• PC Card bus
– Used on laptops to plug in a credit-card sized device
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Computer Processing Speeds
• Instruction speeds measured in fractions of
seconds
– Millisecond: one thousandth of a second
– Microsecond: one millionth of a second
– Nanosecond: one billionth of a second
• Modern computers have reached this speed
– Picosecond: one trillionth of a second
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Microprocessor Speeds
• Measure of system clock speed
– How many electronic pulses the clock produces
per second
– Usually expressed in gigahertz (GHz)
• Billions of machine cycles per second
• Some old PCs measured in megahertz (MHz)
• Comparison of clock speed only meaningful
between identical microprocessors
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Other Performance Measures
• Millions of Instructions per Second (MIPS)
– High-speed personal computers can perform
over 500 MIPS
– Typically a more accurate measure of
performance than clock speed
• Megaflop: one million floating-point
operations
– Measures ability of computer to perform
complex mathematical operations
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Cache
• A temporary storage area
– Speeds up data transfer within computer
• Memory cache
• Processor cache
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Memory Cache
• A small block of high-speed memory
– Stores most frequently and most recently used data and
instructions
• Microprocessor looks for what it needs in cache first
– Transferring from cache is much faster than from memory
– If not found in cache, control unit retrieves it from memory
• The more cache “hits”, the faster the system performance
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Processor Cache
• Internal (Level 1) cache built into
microprocessor
– Fastest access, but highest cost
• External (Level 2) cache on separate chip
– Incorporated into processor on some current
microprocessors
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RISC Technology
• Reduced Instruction Set Computing
– Uses a small subset of instructions
– Fewer instructions increases speed
– Drawback: complex operations have to be
broken down into a series of smaller
instructions
• Traditional processors use Complex
Instruction Set Computing (CISC)
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Parallel Processing and Pipelining
• Pipelining
– A variation of traditional serial processing
• Parallel Processing
– Using multiple processors at once
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Pipelining
• Feeds a new instruction into CPU at each step of the
machine cycle
– Instruction 2 fetched when instruction 1 is being decoded,
rather than waiting until cycle is complete
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Parallel Processing
• Control processor divides problem into
parts
– Each part sent to separate processor
– Each processor has its own memory
– Control processor assembles results
• Some computers using parallel processing
operate in terms of teraflops: trillions of
floating-point instructions per second
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References
• Capron, H. L. (2000). Computers Tools for an Information Age.(6th
ed.). New Jersey, USA: Prentice Hall.
• http://homepage.cs.uri.edu/faculty/wolfe/book/Readings/Reading04.ht
m
• http://en.wikipedia.org/wiki/Pulse_%28signal_processing%29
• http://www.yale.edu/pclt/PCHW/clockidea.htm
• http://www.camiresearch.com/Data_Com_Basics/data_com_tutorial.ht
ml
• http://en.wikipedia.org/w/index.php?title=Relational_operator
• http://en.wikipedia.org/wiki/Word_(computing)
• http://en.wikipedia.org/wiki/32-bit
• http://tldp.org/HOWTO/Unix-and-Internet-FundamentalsHOWTO/core-formats.html
• http://www.indexoftheweb.com/Computer/CPU_Manufacturers.htm
• http://www.theregister.co.uk/2011/06/30/isuppli_q1_2011_cpu_share/
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