William Stallings Computer Organization and Architecture

Chapter 2
Computer Evolution and
Performance
Key Points


• The evolution of computers has been characterized by increasing processor speed, decreasing component size, increasing memory size and increasing I/O capacity and speed
• Processor speed is as a result of shrinking factor in the processor components; reducing the distance between the components hence, increasing speed. True cause is the organization of the processor e.g. pipelining and parallel execution techniques
• Critical issue here is the balancing of the performance of the various elements

A Brief History of Computers
• First generation – vacuum tubes
 ENIAC The
 Von Neumann Machine
 Commercial computers
• Second generation – Transistors
 The IBM 7094
 Third generation – Integrated Circuits
 Later generations

ENIAC - background
• Electronic Numerical Integrator And Computer
• By John Presper Eckert and Prof. John Mauchly at the
• University of Pennsylvania
• World’s first general-purpose electronic digital computer
• Started 1943
• Trajectory tables for weapons
• Finished 1946
 Too late for war effort
• Used until 1955

ENIAC - details
• Decimal (not binary)
• 20 accumulators, each capable of holding 10 digits each
• Programmed manually by switches
• 8,000 vacuum tubes
• 30 tons
• 15,000 square feet
• 140 kW of power consumption
• 5,000 additions per second

Von Neumann/Turing
• 1945-first publication of the idea; the EDVAC (Electronic Discrete Variable Computer)
• The manual programming was too tedious
• Stored Program concept by John Von Neumann; Alan Turing developed the idea at around the same time
• Main memory storing programs and data -a for suitable for storing in memory alongside data
• ALU operating on binary data
• Control unit interpreting instructions from memory and executing
• Input and output equipment operated by control unit
• Work on the computer begun at the Princeton Institute for Advanced Studies. The computer was named, IAS
• Computer and was completed in 1952
• This is the prototype of all subsequent general-purpose computer

Von Neumann/Turing Components
• A main memory that stores both data and instructions
• An ALU (Arithmetic and Logic Unit) capable of operating on binary data
• A control Unit which interprets the instructions in memory an causes them to be executed
• Input and output (I/O) equipment operated by the control unit

Structure of von Neumann


IAS - details
• 1000 storage locations (words) of 40 bits each; both data and instructions are stored here
• Everything must be in Binary number
• Each number is represented by a sign bit and a 39- bit value (see figure 2.2 on page 19 for the William’s book)
• 2 instructions per word of 20 bits each


IAS - details
• Set of registers (storage in CPU)
• Memory Buffer Register (MBR) contains a word to be stored in memory or is used to receive word from memory
• Memory Address Register(MAR) – specifies the address in memory of the word to be written from or read into the MBR
• Instruction Register(IR) – contains the 8-bit opcode instruction being executed
• Instruction Buffer Register (IBR) – employed to hold temporarily the right-hand instruction from a word memory
• Program Counter (PC)- contains the address of the next instruction-pair to be fetched from memory
• Accumulator (AC) and Multiplier Quotient (MQ) – employed to hold temporarily operands and results of ALU operations; e.g. a*b=c(80bits) so the most significant 40 bits are stored in the
• AC and the least significant stored in MQ

Structure of IAS - detail

Commercial Computers
• 1947 -Eckert-Mauchly Computer Corporation
• UNIVAC I (Universal Automatic Computer)
• US Bureau of Census 1950 calculations
• Became part of Sperry-Rand Corporation
• Late 1950s -UNIVAC II
• Faster
• More memory

• IBM
• Punched-card processing equipment
• 1953 - the 701
 IBM’s first stored program computer
 What does IBM stand for?
 Scientific calculations
• 1955 - the 702
 Business applications
• Lead to 700/7000 series

Transistors
• Replaced vacuum tubes
• Smaller
• Cheaper
• Less heat dissipation
• Solid State device
• Made from Silicon (Sand)
• Invented 1947 at Bell Labs
• William Shockley et al.

Transistor Based Computers
• Second generation machines
• NCR (?) & RCA (?) produced small transistor machines
• IBM 7000
• DEC -1957
 Produced PDP-1

Microelectronics
• Literally - “small electronics”
• A computer is made up of gates, memory cells and interconnections
• These can be manufactured on a semiconductor

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 - cofounder 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
• 1964
• Replaced (& not compatible with) 7000 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
• Multiplexed switch structure

DEC PDP-8
• 1964
• First minicomputer (after miniskirt!)
• Did not need air conditioned room
• Small enough to sit on a lab bench
• $16,000
 $100k+ for IBM 360
• Embedded applications & OEM
• BUS STRUCTURE
•

DEC -PDP-8 Bus Structure

Intel
• 1971 - 4004
 First microprocessor
 All CPU components on a single chip
 4 bit
• Followed in 1972 by 8008
 8 bit
 Both designed for specific applications
• z1974 - 8080
 Intel’s first general purpose microprocessor

Designing for Performance
• The cost of computers continue to drop while the performance and capacity continue to rise
• However, the basic building blocks for today’s computers are virtually the same as those of the IAS computer from over 50 years ago!
• The key idea is therefore the techniques for squeezing performance out of the material.

Microprocessor Speed-
Speeding it up
• Pipelining
• On board cache
• On board L1 & L2 cache
• Branch prediction
• Data flow analysis
• Speculative execution

Performance Mismatch
• Processor speed increased
• Memory capacity increased
• Memory speed lags behind processor speed

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

Internet Resources
• http://www.intel.com/
 Search for the Intel Museum
• http://www.ibm.com
• http://www.dec.com
• Charles Babbage Institute
• PowerPC
• Intel Developer Home