Lecture 2 on Chapter 2
Computer Evolution and Performance
by Sameer Akram
1
The Second Generation: Transistors
• Use of transistors defines the second generation
of computers
• It has become widely accepted to classify
computers into generations based on the
fundamental hardware technology employed.
• Each new generation is characterized by greater
processing performance, larger memory
capacity, and smaller size than the previous one.
The Second Generation: Transistors
 Replacement of vacuum tubes by transistors
 Smaller, Cheaper, Less heat dissipation
 Unlike vacuum tubes, which requires wires,
metal plates, a glass capsule, and a vacuum
 Transistor is a Solid State Device
 Made from Silicon (Sand)
 Invented 1947 at Bell Labs
 By 1950s had launched an electronic revolution
Transistor Based Computers
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Second generation machines
NCR & RCA produced small transistor machines
IBM 7000
DEC - 1957
—Produced PDP-1
The Third Generation: Integrated Circuits
 A single, self-contained transistor is called a
“Discrete Component”
 1950’s and early 1960’s
 Electronic equipment was composed largely of
discrete components – transistors, resistors,
capacitors and so on manufactured separately,
packaged in their own containers and soldered
or wired together onto circuit boards, which
were than installed on computers
 The entire manufacturing process, from
transistor to circuit board, was expensive and
cumbersome
Microelectronics
• Literally - “small electronics”
• The basic elements of digital computer must
perform storage, movement, processing and
control functions
• Only two fundamental types of components
required: Gates and Memory Cells
• A computer is made up of gates, memory cells
and interconnections
• These can be manufactured on a semiconductor
• e.g. silicon wafer
Generations of Computer
• Vacuum tube - 1946-1957
• Transistor - 1958-1964
• Small scale integration - 1965 on
—Up to 100 devices on a chip
• Medium scale integration - to 1971
—100-3,000 devices on a chip
• Large scale integration - 1971-1977
—3,000 - 100,000 devices on a chip
• Very large scale integration - 1978 to date
—100,000 - 100,000,000 devices on a chip
• Ultra large scale integration
—Over 100,000,000 devices on a chip
Moore’s Law
 Increased density of components on chip
 Gordon Moore – co-founder of Intel
 Number of transistors on a chip will double
every year
 Since 1970’s development has slowed a little
• Number of transistors doubles every 18 months
 Cost of a chip has remained almost unchanged
 Higher packing density means shorter electrical
paths, giving higher performance
 Smaller size gives increased flexibility
 Reduced power and cooling requirements
 Fewer interconnections increases reliability
Growth in CPU Transistor Count
IBM 360 series
 By 1964, IBM had a firm grip on the computer market
with its 7000 series of machines
 Announced System/360 family of computers not
compatible with 7000 series
 The 360 was the success of decade and cemented IBM
as dominant computer vendor with a market share
above 70%
 With some modifications and extensions, the
architecture of the 360 remains to this day the
architecture of IBM’s mainframe computers
 Compatible computers was very successful: If a
customer’s needs grew, it was possible to upgrade to a
faster machine with more memory without sacrifying the
investment in al-ready developed software
Characteristics of IBM 360 series
• First planned “family” of computers
—Similar or identical instruction sets
—Similar or identical O/S
—Increasing speed
—Increasing number of I/O ports (i.e. more terminals)
—Increased memory size
—Increased cost
• Differences were achieved based on three factors: basic
speed, size, and degree of simultaneity
• Greater speed in the execution of a given instruction
could be gained by the use of more complex circuitry in
ALU, allowing subroutines to be carried out in parallel
• Another way of increasing speed was to increase the
width of data path between main memory and CPU
DEC PDP-8
• In 1964, PDP-8 from Digital Equipment Corporation
(DEC)
• First minicomputer
• Did not need air conditioned room
• Small enough to sit on a lab bench
• $16,000
—Hundreds of Thousands of Dollars for IBM 360
• Embedded applications & Original Equipment
Manufacturers (OEM)
• About 50,000 machines sold in a dozen years
• In contrast to central-switched architecture used by IBM
for 700/7000 and 360 systems, PDP-8 used BUS
STRUCTURE
DEC - PDP-8 Bus Structure
Console
Controller
CPU
Main Memory
OMNIBUS
I/O
Module
I/O
Module
Intel
 1971 - 4004
— First microprocessor
— All CPU components on a single chip
— Can add two 4-bit numbers and can multiply only by
repeated addition
— Clock Speed 108 KHz
— Bus Width 4 bits
— Number of transistors 2300
— Addressable Memory 640 bytes
Intel – Evolution Parameter – Number of Bits
 Evolution can be seen most easily in the number of bits
that the processor deals with at a time.
 There is no clear-cut measure of this, but perhaps the
best measure is the data bus width: the number of bits
of data that can be brought into or sent out of the
processor at a time.
 Another measure is number of bits in accumulator or in
the set of general-purpose registers.
 Often these measures coincide, but not always
 For example, a number of micro-processors were
developed that operate on 16-bit numbers in registers
but can only read or write 8 bits at a time
Intel
• 1972 - 8008
—First 8 bit processor
—Was almost twice as complex as the 4004
—Both 4004 and 8008 were designed for specific
applications
—Clock Speed 108 KHz
—Bus Width 8 bits
—Number of Transistors 3500
—Addressable Memory 16 KBytes
Intel
• 1974 - 8080
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Intel’s first general purpose microprocessor
8 bit processor
Faster, Richer Instruction Set
Larger Addressing Capability
Addressable Memory 64 Kbytes
Number of Transistors 6000
Clock Speed 2MHz
Intel
• 8086
— introduced in 1978
—16 bit processor
— Bus Width 16 bits
— Number of transistors 29,000
— Addressable Memory 1 MB
— Clock Speeds 5 MHz, 8 MHz, 10 MHz
Intel
• 1981
— Bell Labs and Hewlett-Packard developed 32-bit
single chip microprocessors
• 1985 - 80386
— 32 bit processor by Intel
Speeding it up
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Pipelining
On board cache
On board L1 & L2 cache
Branch prediction
Data flow analysis
Speculative execution
Speeding it up
• Branch prediction
The processor looks ahead in the instruction
code fetched from memory and predicts which
branches, or groups of instructions, are likely to
be processed next. If the processor guesses
right most of the time, it can prefetch the
correct instructions and buffer them so that the
processor is kept busy
Speeding it up
• Data flow analysis
The processor analyzes which instructions are
dependent on each other’s results, or data, to
create an optimized schedule of instructions. In
fact, instructions are scheduled to be executed
when ready, independent of original program
order. This prevents unnecessary delay.
Performance Mismatch
• Processor speed increased
• Memory capacity increased
• Memory speed lags behind processor speed
DRAM and Processor Characteristics
Solutions
• Increase number of bits retrieved at one time
—Make DRAM “wider” rather than “deeper”
• Change DRAM interface
—Cache
• Reduce frequency of memory access
—More complex cache and cache on chip
• Increase interconnection bandwidth
—High speed buses
—Hierarchy of buses
Pentium Evolution (1)
• 8080
— first general purpose microprocessor
— 8 bit data path
— Used in first personal computer – Altair
• 8086
— much more powerful
— 16 bit
— instruction cache, prefetch few instructions
— 8088 (8 bit external bus) used in first IBM PC
• 80286
— 16 Mbyte memory addressable
— up from 1Mb
• 80386
— 32 bit
— Support for multitasking
Pentium Evolution (2)
• 80486
—sophisticated powerful cache and instruction
pipelining
—built in maths co-processor
• Pentium
—Superscalar
—Multiple instructions executed in parallel
• Pentium Pro
—Increased superscalar organization
—Aggressive register renaming
—branch prediction
—data flow analysis
—speculative execution
Pentium Evolution (3)
• Pentium II
—MMX technology
—graphics, video & audio processing
• Pentium III
—Additional floating point instructions for 3D graphics
• Pentium 4
—Note Arabic rather than Roman numerals
—Further floating point and multimedia enhancements
• Itanium
—64 bit