1

Lecture 2 on Chapter 2Computer Evolution and Performance

by Sameer Akram

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• 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

OMNIBUS

ConsoleController

CPU Main Memory I/OModule

I/OModule

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— 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• 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