CCS 1202

COMPUTER ORGANIZATION AND ARCHITECTURE

INTRODUCTION
What is Computer Architecture and Organization?
• In general terms, the architecture of a computer system can be considered
as a catalogue of tools or attributes that are visible to the user such as
instruction sets, number of bits used for data, addressing techniques, etc.
• Computer Architecture focuses on the design and structure of a computer
system from the user’s perspective, i.e., the interface and the instruction
set architecture (ISA).

• Whereas, Organization of a computer system defines the way system is

structured so that all those catalogued tools can be used. The significant
components of Computer organization are ALU, CPU, memory and memory
organization.
• Computer Organization is concerned with how the system is implemented
and how the various components (hardware) are connected.
What is Computer Architecture?
Computer Architecture covers all three aspects of computer design
• Instruction Set Architecture
• the computer visible to the assembler language programmer or compiler
writer (registers, data types, instruction set,
instruction formats, addressing modes)
• Organization
• high level aspects of computer’s design such as
the memory system, the bus structure, and
the internal CPU (datapath + control) design
• Hardware
• detailed logic design, interconnection and packing technology, external
connections

3
Computer Architecture Computer Organization
• Attributes of a system • Instruction set, number of
visible to the bits used to represent
programmer various data types, I/O
• Have a direct impact on mechanisms, techniques
the logical execution of for addressing memory
a program Architectural
Computer
attributes
Architecture
include:

Organization
Computer
al attributes
Organization
• Hardware details include:
transparent to the • The operational units and
programmer, control signals, their interconnections that
interfaces between the realize the architectural
computer and peripherals, specifications
memory technology used
 Computer Architecture VS Computer Organization
Computer Architecture Computer Organization
It is concerned with the way hardware It is concerned with the structure and behaviour of
components are connected together to form a a computer system as seen by the user.
computer system.
It acts as the interface between hardware and It deals with the components of a connection in a
software. system.
It helps us to understand the functionalities of a It tells us how exactly all the units in the system
system. are arranged and interconnected.
A programmer can view architecture in terms of Whereas Organization expresses the realization of
instructions, addressing modes and registers. architecture.
While designing a computer system architecture is An organization is done on the basis of
considered first. architecture.
Computer Architecture deals with high-level Computer Organization deals with low-level design
design issues. issues.
Architecture involves Logic (Instruction sets, Organization involves Physical Components (Circuit
Addressing modes, Data types, Cache design, Adders, Signals, Peripherals)
optimization)
 Functions of a Computer
• There are four basic functions that a computer can perform:
• Data processing
• Data may take a wide variety of forms and the range of processing requirements is
broad
• Data storage
• Short-term
• Long-term
• Data movement
• Input-output (I/O) - when data are received from or delivered to a device
(peripheral) that is directly connected to the computer
• Data communications – when data are moved over longer distances, to or from a
remote device
• Control
• A control unit manages the computer’s resources and orchestrates the
performance of its functional parts in response to instructions
The Five Classic Components of a Computer
Input

• Input (mouse, keyboard, …)

• Output (display, printer, …)
• Memory Processor
Output

• main (DRAM), cache (SRAM)

• secondary (disk, Control
Memory
CD, DVD, …) 1001010010110000
0010100101010001

• Datapath Processor 1111011101100110

1001010010110000
Datapath 1001010010110000
• Control (CPU) 1001010010110000
Structure
There are four main  CPU – controls the operation of the computer
structural components and performs its data processing functions
of the computer:
 Main Memory – stores data

 I/O – moves data between the computer and

its external environment

 System Interconnection – some mechanism

that provides for communication among CPU,
main memory, and I/O
 CPU: Major structural components
• Control Unit
• Controls the operation of the CPU and hence the
computer
• Arithmetic and Logic Unit (ALU)
• Performs the computer’s data processing function
• Registers
• Provide storage internal to the CPU
• CPU Interconnection
• Some mechanism that provides for communication
among the control unit, ALU, and registers
 Multicore Computer Structure
• Central processing unit (CPU)
• Portion of the computer that fetches and executes instructions
• Consists of an ALU, a control unit, and registers
• Referred to as a processor in a system with a single processing unit
• Core
• An individual processing unit on a processor chip
• May be equivalent in functionality to a CPU on a single-CPU system
• Specialized processing units are also referred to as cores
• Processor
• A physical piece of silicon containing one or more cores
• Is the computer component that interprets and executes instructions
• Referred to as a multicore processor if it contains multiple cores
 Cache Memory
• Multiple layers of memory between the processor and main memory

• Is smaller and faster than main memory

• Used to speed up memory access by placing in the cache data from

main memory that is likely to be used in the near future

• A greater performance improvement may be obtained by using

multiple levels of cache, with level 1 (L1) closest to the core and
additional levels (L2, L3, etc.) progressively farther from the core
Major elements of a
multicore computer:
Figure 1.3 Motherboard with Two Intel Quad-Core Xeon Processors
 Integrated
Circuits
• A computer consists of gates, memory cells, • Data storage – provided by memory
and interconnections among these elements cells
• The gates and memory cells are constructed • Data processing – provided by gates
of simple digital electronic components • Data movement – the paths among
components are used to move data
• Exploits the fact that such components as from memory to memory and from
transistors, resistors, and conductors can be memory through gates to memory
fabricated from a semiconductor such as
silicon • Control – the paths among
components can carry control signals
• Many transistors can be produced at the
same time on a single wafer of silicon
• Transistors can be connected with a
processor metallization to form circuits
 Moore’s Law
1965; Gordon Moore – co-founder of Intel
Observed number of transistors that could be put on a
single chip was doubling every year

Consequences of Moore’s law:

The pace slowed to
a doubling every 18 Computer
The cost of
months in the The electrical becomes
computer
path length is smaller and is Reduction in
1970’s but has logic and Fewer
shortened, more power and
sustained that rate memory interchip
increasing convenient to cooling
circuitry has connections
ever since fallen at a
operating use in a requirements
speed variety of
dramatic rate
environments
 Microprocessors
• The density of elements on processor chips continued to rise
• More and more elements were placed on each chip so that fewer and fewer
chips were needed to construct a single computer processor
• 1971 Intel developed 4004
• First chip to contain all of the components of a CPU on a single chip
• Birth of microprocessor
• 1972 Intel developed 8008
• First 8-bit microprocessor
• 1974 Intel developed 8080
• First general purpose microprocessor
• Faster, has a richer instruction set, has a large addressing capability
 High-level swap(int v[], int k)

Abstraction language
program
(in C)
{int temp;
temp = v[k];
v[k] = v[k+1];
v[k+1] = temp;
}
• Delving into the depths reveals
more information, but…
C compiler

• An abstraction omits “unneeded”

detail, helps us cope with complexity Assembly
language
swap:
muli $2, $5,4
program add $2, $4,$2
(for MIPS) lw $15, 0($2)
lw $16, 4($2)
sw $16, 0($2)
sw $15, 4($2)
jr $31

• From the figure on the right, how

does abstraction help the programmer Assembler

and how does she/he avoid too much

detail? Binary machine
language
00000000101000010000000000011000
00000000100011100001100000100001
program 10001100011000100000000000000000
(for MIPS) 10001100111100100000000000000100
10101100111100100000000000000000
10101100011000100000000000000100
00000011111000000000000000001000
Levels of
representation
Levels of
Abstraction
The Instruction set
Instruction Set Architecture
• A very important abstraction:
• interface between hardware and low-level software
• standardizes instructions, machine language bit patterns, etc.
• advantage: allows different implementations of the same architecture
• disadvantage: sometimes prevents adding new innovations

• Examples of instruction set architectures:

• 80x86/Pentium/K6, PowerPC, DEC Alpha, MIPS, SPARC, HP
A Safe Place for Data
• Volatile main memory
• Loses instructions and data when power off
• Non-volatile secondary memory
• Magnetic disk
• Flash memory
• Optical disk (CDROM, DVD)
Technology Trends
• Electronics technology
continues to evolve
• Increased capacity and
performance
• Reduced cost
DRAM capacity

Year Technology Relative performance/cost

1951 Vacuum tube 1
1965 Transistor 35
1975 Integrated circuit (IC) 900
1995 Very large scale IC (VLSI) 2,400,000
2005 Ultra large scale IC 6,200,000,000
What does an architect do?

Translates
business and
technology
drivers into
efficient
systems for
computing
tasks
Applications drive design points