Transcript Introduction to Computer Architecture

Introduction to Computer
Architecture
What is binary?
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We use the decimal (base 10) number
system
Binary is the base 2 number system
Ten different numbers are used in
base 10. How many are used in base
2?
Bits & Bytes
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kilo, mega, and giga are different in
binary!
bit (b) – binary digit
Byte (B) – 8 binary digits
KiloByte (KB) – 210 bytes
MegaByte (MB) – 220 bytes
GigaByte (GB) – 230 bytes
Storage Scam!
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Example: iPod Nano 8GB
What is computer
architecture?
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What does “architecture” mean?
Layout and interactions of a computer
system
What is a computer system?
Input  Process  Output
Can a computer system be more than
one computer? Think of an example...
Major Components of a Computer
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Central Processing Unit (CPU)
Random Access Memory (RAM)
Hard Drive / Disk
ON-OFF-ON-ON
1
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0
1
1
Several ways to remember the state of a switch:
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Electrical – RAM, flash memory, ROM
Magnetic – Hard drives, magnetic tapes
Optical – CDs, DVDs
Primary Memory
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Memory level CPU accesses closest
RAM ~ Random Access Memory
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Volatile storage (data is NOT saved when
computer is off)
Used to store everything (OS, programs, etc.)
while computer is on
ROM ~ Read-Only Memory
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Non-volatile storage
Often holds the computer’s BIOS (Basic
Input/Output System) when computer first loads
What does memory look like?
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Memory ~ RAM
Looks like a table
Address and Data
Address is the
location
Data is the actual
value
Memory stores both
data and assembly
instructions
Address
0
1
2
3
4
5
6
7
8
Data
36
3765
786
356
252
67980
2355
4234
3466
Central Processing Unit (CPU)
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Also called the “chip”
or “processor”
The brain of the
computer
Major components:
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Arithmetic Logic Unit
(ALU)
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Control unit
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calculator
controls the calculator
Communication bus
systems
What’s a bus?!?
Control
Unit
Address Bus
Memory
ALU
Data Bus
Fetch-Execute Cycle
(Machine Instruction Cycle)
1.
2.
3.
4.
5.
Fetch instruction from
memory
Decode instruction in
control unit
Execute instruction (data
may be fetched from
memory)
Store results if necessary
Repeat!
Control
Unit
Address Bus
Memory
ALU
Data Bus
Registers
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Temporary storage containers used inside
the CPU
Extremely fast
MAR ~ Memory Address Register
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MDR ~ Memory Data Register
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Holds the address of where you are fetching
from
Holds the data that was fetched from memory
Many other registers too (for all CPU
calculations)
Fetch-Execute Animation
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http://www.hartismere.com/staticvle/ict
skills/FetchExecute.swf
Memory Hierarchy
Cache
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Slower than registers
Faster than RAM
Located in front of
main RAM
Different levels of
cache
Level1 (L1) and Level2
(L2)
Size is usually around
1 MB
Virtual Memory
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What if a program is too big for RAM?
If a program is too big for memory
(RAM), then we start using the hard
drive (disk) to store data
Prevents the computer from
stalling/crashing (BUT IT IS SLOW)
Hard Drives
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Persistent storage
Non-volatile storage
Why do we need it?
Other types of persistent
storage?
CD/DVD/BluRays
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Lands and pits used to represent
binary
Optical medium - lasers and refraction
used to read lands and pits