Department of Computer Science
Faculty of Civil Engineering, Brno University of Technology
Information Technology 1
Inside the
Personal Computer
1
Repetition
2
• A computer is a data processing machine which is
operated automatically under the control of a list
of instructions (called a program) stored in its
main memory.
• Conventional digital computers have a common form
that is attributed to von Neumann.
• Von Neumann computers are general purpose
computers.
• Data and instructions are both stored
in the main memory.
• Central processing unit (CPU, processor) contains the
control unit that coordinates the execution of
instructions, and the arithmetic-logic unit that
performs arithmetic and logic operations.
3
Repetition
Arithmetic-logic
unit
Control unit
Registers
Instructions
Data
Main memory
(operational)
CPU
Repetition
• The main (operational) memory is used to store
program and data which are currently manipulated
by the CPU. Main memory is fast and of limited size.
• The peripheral (secondary) memory provides the
long-term storage of large amounts of data and
program. It is relatively slow and of very large size.
• The most important characteristics of a memory are
speed (access time and data transfer rate), size
and cost, which are mainly constrained
by the technology used for its implementation.
• Facts:
• The faster memory is, the greater the cost/bit is.
• (The larger memory is, the slower is it.)
4
The Anatomy of a PC – Key Concepts
RAM An acronym for Random Access Memory. It is
random because any of the bits or bytes resident
in RAM can be accessed nonseqeuntially. RAM is
memory that can be both read and written to.
The information stored in a semiconductor RAM
will be lost when electrical power is removed.
ROM An acronym for Read-Only Memory. We cannot
write new data to those memories. There are
several subtypes of ROM: “classical” ROM,
PROM (Programmable ROM),
EPROM (Erasable PROM),
EEPROM (Electrically EPROM),
Flash-EEPROM.
5
The Anatomy of a PC – Key Concepts
BIOS An acronym for Basic Input/Output Sytem.
A collection of software codes built into a PC.
BIOS is stored in ROM (Flash-EEPROM usually)
chip on the motherboard.
Boot The process that takes place when a PC is turned
on and it performs the routines necessary to get
all the components functioning properly and then
load the operating system.
POST An acronym for Power-On Self-Test, a procedure
the computer goes through when booting to
verify that the basic components of a PC are
functioning.
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The Anatomy of a PC – Key Concepts
7
CMOS An acronym for Complementary Metal-Oxide
Semiconductor – a term that describes how
a CMOS chip is manufactured. Powered by
a small battery, the CMOS memory chip retains
crucial information about what hardware a PC
comprises even when the power is turned off.
Clock A microchip that regulates the timing and speed
of all the computer’s functions. The chip includes
a crystal that vibrates at a certain frequency when
electricity is applied to it. The speed of clocks –
– and therefore computers – is expressed in
megahertz (MHz) or gigahertz (GHz). Thus a PC
may be desribed as having a 1.2 GHz processor,
which means that the processor has been designed
to work with a clock chip runnig at that speed.
Types of RAM
• DRAM (Dynamic Random Access Memory)
For years, the most common type of main RAM.
“Dynamic” refers to the memory's method of
storage – basically storing the charge on
a capacitor, which leaks the charge over time and
must be refreshed about every thousandth
of a second.
• SRAM (Static Random Access Memory)
RAM that, unlike DRAM, doesn't need to have its
electrical charges constantly refreshed. SRAM is
usually faster than DRAM but more expensive.
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Memory Modules
Memory module is a small circuit board with the
memory chips (RAM). It uses less board space and
it is more compact.
• SIMM (Single In-Line Memory Module) 30- or 72-pin
• DIMM (Dual In-Line Memory Module)
• RIMM (Rambus In-Line Memory Module)
9
10
Memory Modules – cont‘d
SIMM (72-pin)
DIMM
Cache Memory
• The speed of the main memory is relative slow with
respect to the today's processors.
• A cache memory is a small, very fast memory that
retains copies of recently used information from the
main memory.
• Memory caching is effective because the running
programs access the same data or instructions over
and over.
• Cache capacity is much smaller than main memory
(about 1/128 – 1/32 of the main memory capacity).
• Cache memory operates transparently to the
programmer, automatically deciding which values to
keep and which values to overwrite.
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Cache Memory – cont‘d
• Primary cache (Level 1, L1 cache) is built into the
processor chip with a zero wait-state (delay)
interface to the processor's execution unit, it is
limited in size.
• Secondary cache (Level 2, L2 cache) can be found
on the motherboard.
12
CPU (processor, microprocessor)
13
• CPU – Central Processing Unit
• often called the brains of a computer
• CPU is a tight, complex collection of transistors
arranged so that they can be used to manipulate data
• most operations of the computer are handled by the
processor
• processor manufacturers:
Intel, AMD, Cyrix
CPU – cont'd
According to Moore's Law formulated in 1965 by
Gordon Moore (co-founder of Intel), the number
of transistors per integrated circuit would double
every 18 months. Moore predicted that this trend
would hold for the next ten years. In fact, as the
graph illustrates, Intel has managed to doggedly
follow this law for far longer. In 1978 the 8086 ran
at 4.77 MHz and had less than 30,000 transistors.
By the end of the millennium the Pentium 4 had
a staggering 42 million on-chip transistors and
ran at 1.5 GHz.
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CPU – cont'd
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Source: www.pctechguide.com
Processor Registers
16
• Registers are very fast temporary storage devices
typically used to hold intensively used data and
intermediate results.
• The set of registers within the CPU represents the top
level of the memory hierarchy.
User Visible Registers
• Can be accessed by programmers.
• They are often called general-purpose registers.
Control and Status Registers
• Used by the control unit to control the operation of the
CPU; not directly accessible by the programmer.
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Stack
• A list of data elements, with the restriction that
elements can be added or removed at one end of the
list only. This end is called the top of the stack and
the other end is called the bottom.
• Placing a new element on top of the stack is an
operation called push; removing the top element is
called pop.
• LIFO – Last In First Out
5
4
3
2
1
5
4
3
2
1
„Generations of Processors“
Type/Generation
Year
8086/First
8088/First
80286/Second
80386DX/Third
80386SX/Third
80486DX/Fourth
80486SX/Fourth
80486DX2/Fourth
80486DX4/Fourth
Pentium/Fifth
Pentium MMX/Fifth
Pentium Pro/Sixth
Pentium II/Sixth
Pentium II/Sixth
Pentium III/Sixth
AMD Athlon/Seventh
Pentium 4/Seventh
1978
1979
1982
1985
1988
1989
1989
1992
1994
1993
1997
1995
1997
1998
1999
1999
2000
Data/
Address
Bus
16/20 bit
8/20 bit
16/24 bit
32/32 bit
16/32 bit
32/32 bit
32/32 bit
32/32 bit
32/32 bit
64/32 bit
64/32 bit
64/36 bit
64/36 bit
64/36 bit
64/36 bit
64/36 bit
64/36 bit
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L1
Memory Internal
Cache Speed
Clock
[KB]
[MHz]
[MHz]
None
4.77-8
4.77-8
None
4.77-8
4.77-8
None
6-20
6-20
None
16-33
16-33
8
16-33
16-33
8
25-50
25-50
8
25-50
25-50
8
25-40
50-80
8+8
25-40
75-120
8+8
60-66
60-200
16+16 66
166-233
8+8
66
150-200
16+16 66
233-300
16+16 66/100
300-450
16+16 100
450-600
64+64 100-200+ 500-600+
12+8
100
1.4 – 2 GHz
Block Diagram of the 8086 Processor
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20
AMD Processors
Athlon
Duron
K6-2
Motherboard (mainboard)
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The main circuit board inside the PC which holds
• processor,
• main (operational) memory – RAM,
• CMOS memory (it is used to store basic information about
the PC's configuration)
• BIOS stored in ROM (usually Flash-EEPROM)
• integrated floppy drive and hard drive controller
• expansion slots (ISA, PCI, AGP, ...)
• I/O ports and other interfaces (parallel and serial port,
USB, …)
• connectors to connect other parts of a computer
(keyboard, small speaker, reset switch,
power LED, CPU fan, …)
...
The above-stated information is dependent on the type of motherboard.
Motherboard (mainboard) – cont'd
Graphics card, soundcard, faxmodem, etc. can
be integrated on the motherboard (“All-In-One”
motherboard).
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Expansion (I/O) Buses
• peripherals are connected to the I/O buses in
various ways, primarily through connectors directly
on the motherboard and through different
interfaces such as expansion cards
• I/O bus depends on the type of processor
• slots (connectors of I/O bus) are placed on the
motherboard
• different types of I/O buses:
ISA, MCA, EISA, VL-Bus, PCI, AGP
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ISA Expansion Bus
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ISA – Industry Standard Architecture (also AT-Bus)
• the oldest, slowest and soon to become obsolete
I/O bus
• designed for 80286 processor
• specifies a 16-bit transfer driven by a 8 MHz clock
• It has a theoretical data transfer rate of up to
16 MBps. Functionally, this rate would reduce by a half
to 8 MBps since one bus cycle is required for
addressing and a further bus cycle for the 16-bits
of data. In the real world it is capable of more like
5 MBps - still sufficient for many peripherals - and the
huge number of ISA expansion cards ensured its
continued presence into the late 1990s.
Block Diagram of the ISA Architecture
(simplified)
Processor
ISA
controller
Main
memory
System
bus
8-bit
slots
16-bit
slots
ISA Bus
L2
cache
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PCI Expansion Bus
26
PCI – Peripheral Component Interconnect
• designed for 80486 a Pentium processors
• in its original implementation PCI ran at 33 MHz,
it was later raised to 66 MHz
• theoretical throughput to 266 MBps (33 times faster
then ISA)
• it can be configured both as a 32-bit and a 64-bit bus
• supports the PnP standard (Plug and Play)
Block Diagram of the PCI Architecture
(simplified)
PCI slots
PCI/ISA
Bridge
CPU/PCI
Bridge
Processor
System
bus
ISA slots
ISA Bus
PCI bus
Main
memory
L2
cache
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28
PCI Slots
ISA Slots
Source: www.howstuffworks.com
AGP
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AGP – Accelerated Graphics Port
• designed for Pentium II processor
• used for graphics cards only
• significantly speeds the performance in graphics app's
(3D graphics, texture mapping and so on)
• operates at the speed of the processor bus
• AGP 1x (264 MBps),
AGP 2x (528 MBps),
AGP 4x (1056 MBps)
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Block Diagram of the AGP Architecture
Source: www.pctechguide.com
AGP-based Graphics Card (example)
Source: www.howstuffworks.com
31
Parallel Port
• is most often used to connect a printer
• some drives (e.g. ZIP) and other peripherals (e.g.
scanner) may piggyback on the parallel port
• Canon connector, 25-pin female, marked LPT or PRN,
(interface Centronics)
• standard IEEE 1284 provides bi-directional
communication and faster data flow
• Compatible Mode (Centronics), Nibble Mode,
Byte Mode, EPP (Enhanced Parallel Port) Mode,
ECP (Extended Capabilities Port) Mode
• EPP mode is mostly used
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Serial Port
33
• is most often used to connect a mouse or a modem
• Canon connector, 9- (or 25-) pin male, marked COM
or RS 232
• slower than parallel port
• today's computers usually use a mouse that connects
to a PS/2 port (connector)
USB
• USB – Universal Serial Bus
• up to 127 peripheral devices can be connected
• supports fast data transfer rates
• along with the signal USB carries a 5 V power supply
so small devices, such as hand held scanners or
speakers, do not have to have their own power cable
• was designed to be user-friendly
and it is truly PnP
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Motherboard SL-77KV
Specification
www.soltek.com.tw
Processor: AMD Athlon™
Chipset: VIA APOLLO KX133, FSB 200 MHz, AGP 4x
Memory: 3 x 168-pin 3.3V DIMM Sockets,
Supports 8MB to 768MB (maximum) DRAM Size,
PC 133 compliant
Cache Memory:
Built-in to AMD Athlon™ Processor Module
On-Board EIDE:
2 x PCI Bus Master UATA 33/66 IDE ports
(up to 4 ATAPI Devices)
Supports for PIO Mode 3, 4,
UATA 33/66 IDE & ATAPI CD-ROM
Motherboard SL-77KV – cont'd
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On-Board Super I/O: 1 x Floppy Port,
2 x serial ports (high-speed 16550 FIFO UART Ports),
1 x Parallel Port with EEP/ECP/SPP Capabilities,
PS/2 Mouse connector, Keyboard connector,
4 x USB Ports
Expansion Slots: 1 x AGP Slot, 1 x AMR Slot,
5 x 32-bit PCI Bus Master Slots, 1 x 16-bit ISA Slots
Form Factor: ATX Form Factor (190mm x 305mm)
BIOS: AWARD Plug-and-Play BIOS
Supports Advanced Power Management Function
Flash Memory for easy upgrade
Other Features: Supports AGP4x, PC 133 compliant,
Ultra ATA/66, AC'97 Audio Function, H/W Monitor
Motherboard SL-77KV – cont'd
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Motherboard SL-77KV – cont'd
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Power Supply
• converts the AC input (230 V) to lower DC voltages
(3.3 V, 5 V, 12 V, –5 V, –12 V)
• 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
• the main specification
of a power supply
is in watts
(usually about
250 W or more)
Source: www.howstuffworks.com
39
40
Power Supply – cont'd
According to PC Power & Cooling, Inc., some power
consumption values (in watts) for common items in
a personal computer are:
AGP card
PCI card
floppy disk drive
network interface card
50x CD-ROM drive
RAM
5200 RPM IDE hard disk drive
7200 RPM IDE hard disk drive
Motherboard (without CPU or RAM)
550 MHz Pentium III
733 MHz Pentium III
300 MHz Celeron
600 MHz Athlon
20 to 30 W
5W
5W
4W
10 to 25 W
10 W per 128 MB
5 to 11W
5 to 15W
20 to 30W
30W
23.5W
18W
45W
Input/Output Processing
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1. Programmed I/O
• The CPU executes a sequence of instructions, being
in direct control of the I/O operations (sensing device
status, read/write commands, etc.).
• When the CPU issues a command to the I/O module,
it must wait until the I/O operation is complete.
• A lot of waisted time, because the CPU is much
faster then devices.
Input/Output Processing
42
2. Interrupt-driven I/O
• IRQ – Interrupt Request
• After issuing an I/O command, the CPU has not to wait
until the operation has finished; instead of waiting,
the CPU continues with other useful work.
• When the I/O operation has been completed, the I/O
module issues an interrupt signal on the bus.
• After receiving the interrupt, the CPU moves the data
to/from memory, and issues a new command if more
data has to be read/written.
Input/Output Processing
43
2. Interrupt-driven I/O – cont'd
Advantage over programmed I/O:
• Instead of waiting the operation to be finished,
the CPU can do some useful work.
Still a problem:
• If large amounts of data have to be moved, this
technique is still not efficient, because the CPU has
to take care of each data unit separately, to move
it to/from memory.
• Handling the interrupt also takes some time.
Input/Output Processing
3. Direct Memory Access (DMA)
• An additional module on the system bus, the DMA
module (controller), takes care of the I/O transfer
for the whole sequence of data.
• The CPU issues a command to the DMA module and
transfers to it all the needed information.
• The DMA module performs all the operations – it
transfers all the data between I/O module and
memory without going through the CPU.
• When the DMA module has finished, it issues an
interrupt to the CPU.
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Device Manager – MS Windows 2000
45
References
• http://www.pctechguide.com
• http://www.howstuffworks.com
• http://www.zive.cz
• White, R.: How computers work. Que, Indianapolis 1999.
• Vrátil, Z.: Postavte si PC. BEN, Praha 1999.
• Horák, J.: Učebnice hardware. Computer Press,
Praha 1998.
• Precht, M. – Meier, N. – Kleinlein, J.:
EDV-Grundwissen: Eine Einführung in Theorie und
Praxis der modernen EDV. Addison-Wesley, 1996.
• Колесниченко, О. – Шишигин, И.: Аппаратные
средства РС. «БХВ», Санкт-Петербург 1999.
• Вильховченко, С.: Современный компьютер:
устройство, выбор, модернизация. «Питер»,
Санкт-Петербург 2000.
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