1. Lecture 2 on Chapter 2 Computer Evolution and Performance
by Sameer Akram

2. 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.

3. 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

4. Transistor Based Computers
Second generation machines
NCR & RCA produced small transistor machines
IBM 7000
DEC
Produced PDP-1

5. 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

6. 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

7. Generations of Computer
Vacuum tube
Transistor
Small scale integration on
Up to 100 devices on a chip
Medium scale integration - to 1971
100-3,000 devices on a chip
Large scale integration
3, ,000 devices on a chip
Very large scale integration to date
100, ,000,000 devices on a chip
Ultra large scale integration
Over 100,000,000 devices on a chip

8. Increased density of components on 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

9. Growth in CPU Transistor Count

10. 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

11. 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

12. 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

13. DEC - PDP-8 Bus Structure
I/O
Module
Main Memory
I/O
Module
Console
Controller
CPU
OMNIBUS

14. 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

15. 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

16. 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

17. 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

18. 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

19. Intel
1981
Bell Labs and Hewlett-Packard developed 32-bit single chip microprocessors
32 bit processor by Intel

20. Speeding it up
Pipelining
On board cache
On board L1 & L2 cache
Branch prediction
Data flow analysis
Speculative execution

21. 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

22. 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.

23. Performance Mismatch
Processor speed increased
Memory capacity increased
Memory speed lags behind processor speed

24. DRAM and Processor Characteristics

25. Increase number of bits retrieved at one time Change DRAM interface
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

26. 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

27. Pentium Evolution (2) 80486 Pentium Pentium Pro
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

28. Pentium Evolution (3) Pentium II Pentium III Pentium 4 Itanium
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