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L07 – Architectural Components
ARCHITECTURAL
COMPONENTS
Reading: Chapter 4
(sections 4.1 – 4.7)
ISE218 – Fundamentals of Information Technology
© Robert F. Kelly, 2012-2016
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Objectives
• Learn the common computer components
• Understand how each component contributes to
program execution
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CPU
• Programs and data are both stored in
memory
• The computer’s Central Processing
Unit (CPU) fetches, decodes, and
executes program instructions
• The principal parts of most CPUs are
• Arithmetic logic unit (ALU)
• Registers
• Control unit
• Internal bus
© Robert F. Kelly, 2012-2016
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ALU
• Performs operations
• Addition
• Multiplication
• Comparison
• The control unit tells the ALU which operations to
perform
• Operations synchronized by the clock
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Registers
• Very fast memory
• Located very close to the
ALU
• Processors vary in
• Number of registers
• Type of registers (e.g.,
address, integer, floating point,
general purpose)
• Bits in each register
• Example – register used to
hold an instruction loaded
from memory
© Robert F. Kelly, 2012-2016
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Control Unit
• The control unit
• Monitors the execution of
instructions
• Coordinates traffic to and from
the CPU
• Decodes instructions
• Controls the ALU
• Includes a program counter
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Internal Computer Bus
• Allows CPU components to communicate
© Robert F. Kelly, 2012-2016
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CPU Basics
• Registers hold data that can be
readily accessed by the CPU
• The arithmetic-logic unit (ALU)
carries out logical and arithmetic
operations as directed by the
control unit
• The control unit determines
which actions to carry out
according to the values in a
program counter register and a
status register
e.g., ALU does
2’s complement
addition
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Printed Circuit Board (PCB)
• Keeps computer system components in place
• electrically connects electronic components
• Contains conductive tracks
• More reliable than wiring
components
© Robert F. Kelly, 2012-2016
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Motherboard
• The central printed circuit board
(PCB) in many modern
computers
• Holds many of the crucial
components of the system
• provides connectors for
other peripherals.
• Alternatively known as the
mainboard, system board, or, on
Apple computers, the logic
board
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Motherboard Components*
• Sockets (or slots) in which one or
Relates mainly to
desktops and servers
more microprocessors may be installed
• Slots into which the system's main memory is
installed
• A chipset - forms an interface between the CPU's
front-side bus, main memory, and peripheral buses
• Non-volatile memory chips (firmware or BIOS)
• Clock generator
• Slots for expansion cards (these interface to the
system via the buses supported by the chipset)
Recent motherboards include
• Power connectors
* From Wikipedia
integrated controllers
(e.g., sound, graphics, network)
© Robert F. Kelly, 2012-2016
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CPU Socket
• Allows the CPU to be
replaced without soldering
• Functions:
• a physical structure to support
the CPU
• support for a heat sink
• forms an electrical interface both
with the CPU and the PCB
Also referred
to as a slot
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© Robert F. Kelly, 2012-2016
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Connectors
• Transmit
information from
one part of a
computer to another
The Bus
The bus connecting the CPU and
memory is called the system bus
• The system shares data with other system
components by way of a data bus
PCI bus slots
provide
attachment for
expansion cards
Increasingly
integrated into
motherboards or
by USB devices
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Bus Details
• A set of connections that
connect multiple subsystems
within a computer
• Usually connects multiple
components
• Connections for addresses,
data, and control
• Uses a bus protocol
Bus protocol is the
set of rules for
moving data
between devices
In a computer with 2n memory
addresses, how wide is the address bus?
© Robert F. Kelly, 2012-2016
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Clocks
• Every computer contains at least one clock that
synchronizes the activities of its components
• A fixed number of clock cycles are required to
carry out each data movement or computational
operation
• The clock frequency, measured in megahertz or
gigahertz, determines the speed with which
operations are carried out
• Clock cycle time is the reciprocal of clock
frequency
• An 800 MHz clock has a cycle time of 1.25 ns
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Clocks
• Clock speed is related to CPU performance – but
not an exact relationship
• Improve CPU performance throughput by
reducing
• the number of instructions in a program,
• the number of cycles per instruction, or
• the number of nanoseconds per clock cycle
Other “superscalar”
approaches are possible
© Robert F. Kelly, 2012-2016
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Are We on Track?
• What is the approximate instruction rate of the
Apple iPhone 6 processor (Apple A9) in GHz?
And how many processors?
2 processors, 1.85 GHz
• What is the approximate instruction rate of the
Samsung Galaxy S5? And how many
processors?
4 processors at 2.1 GHz and
4 processors at 1.5 Ghz
Most people refer to the processor rate on a
multi-core processor as the per-processor rate
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© Robert F. Kelly, 2012-2016
Are We on Track?
• Is a 1GHz dual core processor as powerful as a
2GHz single core processor?
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© Robert F. Kelly, 2012-2016
Memory Notation
• L x W (length x width)
Each byte is
addressable
• Example – 4K x 8
• Memory has 4K (212) addressable locations
• Each addressable location is 8 bits wide (byte
addressable)
Address
Data
0000 0000 0000
0
1
1
0
0
1
1
0
0000 0000 0001
0
0
0
0
0
0
0
0
0000 0000 0010
0
0
0
0
0
0
0
0
0000 0000 0011
1
1
1
0
0
0
0
0
1
1
0
0
0
0
0
0
…
1111 1111 1111
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Memory Organization
• Computer memory consists of a linear array of
addressable storage cells
• Memory can be byte-addressable, or wordaddressable, where a word typically consists of
two or more bytes
• If the memory word size of the machine is 16 bits,
then a 4M × 16 RAM chip gives us 4M of 16-bit
memory locations
© Robert F. Kelly, 2012-2016
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Addressing Memory
• 4M can be expressed as
212 (4,096) × 210 (1,024) = 222 addressable words
• The memory locations for this memory are
numbered 0 through 222 -1
• Thus, the memory bus of this system requires at
least 22 address lines
• The address lines “count” from 0 to 222 - 1 in binary
• Each line is either “on” or “off” (1 or 0),
indicating the address of the desired memory element
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Address Lines
• Addresses and data are usually transmitted
in parallel
© Robert F. Kelly, 2012-2016
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Memory Addressing Example
• If memory contains:
Memory Size
Memory
Addresses
Address Size
2 bytes
0 and 1
1 bit
4 bytes
00, 01, 10, 11
2 bits
8 bytes
000, 001, 010,
011, 100, 101,
110, 111
3 bits
2n
00000, 00001, …
n bits
e.g., n=5
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© Robert F. Kelly, 2012-2016
Memory Organization
• Physical memory usually consists of more than
one RAM chip
• Access is more efficient when memory is
organized into banks of chips with the addresses
interleaved across the chips
• Low-order interleaving - low order bits of the address
specify which memory bank contains the address of
interest
• High-order interleaving - high order address bits specify
the memory bank
1
0
1
1
0
1
0
1
1
© Robert F. Kelly, 2012-2016
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Are We On Track?
• How many bits are required to address an 8G x
16 main memory if
• Main memory is byte-addressable?
• Main memory is word-addressable?
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Were We on Track?
• How many bits are required to address an 8G x
16 main memory if
• Main memory is byte-addressable?
• Main memory is word-addressable?
• Memory contains 16GB
• If each byte is addressable, there are 16G
addresses or 24 * 230 = 234 addresses, which
requires 34 bits
• If each word is addressable, we only need 33 bits
for the address
© Robert F. Kelly, 2012-2016
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Interrupts
• The normal execution of a program is altered
when an event of higher-priority occurs
• CPU is alerted to an event through an interrupt
• Interrupts can be triggered by I/O requests,
arithmetic errors (such as division by zero), or
when an invalid instruction is encountered
• Each interrupt is associated with a procedure that
directs the actions of the CPU when an interrupt
occurs
• Non-maskable interrupts are high-priority interrupts that
cannot be ignored.
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The Input/Output Subsystem
• A computer communicates with the outside world
through its input/output (I/O) subsystem
• I/O devices connect to the CPU through various
interfaces
• I/O can be memory-mapped-- where the I/O
device behaves like main memory from the
CPU’s point of view
• Or I/O can be instruction-based, where the CPU
has a specialized I/O instruction set
© Robert F. Kelly, 2012-2016
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Did You Satisfy the Objectives?
• Learn the common computer components
• Understand how each component contributes to
program execution
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