Lecture 2 on Chapter 2 Computer 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

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

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 I/O Module Main Memory I/O Module Console Controller CPU OMNIBUS

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

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

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 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

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