IS 139 Lecture 1 - UDSM - 2014

2. Overview - 1
 How does a computer work?
 How components fit together
 Control signals, signaling methods, memory types
 How do I design a computer?
 Structure and behavior of computer systems
 ISA – instruction sets and formats, op codes, data
types, no. and type of registers, addressing modes,
memory access methods, I/O mechanisms

3. Overview - 2
 It’s all about function & structure
 Structure => the way in which components are
interrelated
 Function => the operation of each individual
component

4. Overview - 2
 Architecture vs organization
 Architecture = attributes visible to programmers e.g.
instruction set, I/O mechanisms, addressing modes
 Organization = units & their interconnections that
realize architectural specs e.g. control signals, I/O
interfaces, memory technology used
 Manufacturers offer family of models => same
architecture but different organizations

5. Why study computer
architecture?
 Program optimization – understanding why a
program/algorithm runs slow
 Understanding FP arithmetic crucial for large, real
world systems
 Design of peripheral systems i.e. device drivers
 Design tradeoffs of embedded systems

6. Why study computer
architecture?
 Benchmarking
 Building better compilers, OS’s
 Writing software that takes advantage of hardware
features - parallelism

7. You should be able to
 Understand how programs written in high level
languages get translated & executed by the H/W
 Determine the performance of programs and what
affects them
 Understand techniques used by hardware designers
to improve performance
 Evaluate and compare the performance of different
computing systems

8. General purpose
computers
 Software and hardware are interrelated
 “Anything that can be done with software can also
been done with hardware, and anything that can be
done with hardware can be done with software” –
Principal of Equivalence of H/W and S/W
 This observation allows us to construct general
purpose computing systems with simple instructions

9. Functions of general purpose
computer
 Data processing
 Data can take various forms
 Data storage
 Temporarily or long term
 Data movement
 Between itself & outside world
 Control
 Orchestrates the different parts

10. Computer Organization & architecture - Stallings

11. What makes a computer?
 Processor – data path & control
 Memory
 Mechanism to communicate with the outside world
 Input
 Output

12. Organization of a
computer
Computer Organization & design - Patterson

13. Classes of computers
 Desktop computers
 Familiar to most people
 Features: good performance, single user, execution of third party software
 Servers
 Hidden from most users – accessible via a network – Cloud computing – in data
centers
 Features: handling large workloads, dependability, expandability
 From cheap low ends to extreme super computers with thousands of processors
used for forecasting, oil exploration
 Embedded computers
 The largest class – wide range of applications & performance
 In cars, cell phones, video game consoles, planes
 Focus in limitation of power and cost

14. Growth of embedded
computers in cell phones

15. Tons of features
The essentials of Computer organization & architecture - Null

16. A look inside
The essentials of Computer organization & architecture - Null

17. How did we get here?
 A lot has happened in the 60+ year life span
 E.g. if transportation industry developed at same
pace – here to London in 1 sec for a few cents
 Different generations in the evolution of computers
 Each generation defined by a distinct technology
used to build a computer at that time
 Why? – gives perspective & context into design
decisions, understand why things are as they are

18. Generation 0: Mechanical
Calculating Machines - 1
 Defining characteristic - mechanical
 1500s
 There was a need to make decimal calculations faster
 Mechanical calculator (Pascaline) – Blaise Pascal
 No memory, not programmable
 Used well into 20th century
 Difference Engine – Charles Babbage “Father of
Computing”
 Used method of difference to solve polynomial functions
 Was still a calculator

19. Generation 0: Mechanical
Calculating Machines - 2
 Analytical engine – an improvement over “Difference
Engine” – It was a significant development
 More versatile – capable of performing any math operation
 Similar to modern computers – mill (processor), store
(memory) & input/output devices
 Conditioning branch op – next instruction depending on
previous
 Ada, Countess of Lovelace suggested a plan for how the
machine should calculate numbers – The first programmer
 Used punch cards for input & programming – this method
survived for a long time

20. Generation 0
 Drawbacks
 Slow – limited by the inertia of moving parts (gears &
pulleys)
 Cumbersome, unreliable & expensive

21. 1st Generation: Vacuum Tube
Computers (1945 -1953)
 Defining characteristic: use of vacuum tubes as switching
technology
 Previous generations were mechanical but not electrical
 Konrad Zuse – in 1930s added electrical tech & other
improvements to Babbage’s design
 Z1 used electromechanical relays – was programmable,
had memory, arithmetic unit, control unit
 Used discarded film for input

22. 1st Generation
 John Atanasoff, John Mauchly, J. Presper Eckert –
credited with the invention of digital computers;
However many others contributed
 Their work resulted in ENIAC (Electronic numerical
Integrator and Computer) in 1946 – the first all
electronic, general purpose digital computer
 Was built to facilitate weather prediction but ended
up being financed & by the US army for ballistic
trajection calculations

24. 2nd Generation: Transistorized
Computers (1954 – 1965)
 Defining characteristic: Use of transistor as switching
technology
 Vacuum tube tech was not very dependable – they tended to
burn out
 In 1948 at Bell Laboratories – John Bardeen, Walter Brattain &
William Shockley invented the TRANSISTOR
 Was a revolution – Transistors are smaller, more reliable,
consume less power
 Caused circuitry to become more smaller & more reliable
 Emergence of companies such as IBM, DEC & Unisys

25. 3rd Generation: Integrated Circuit
Computers (1965 – 1980)
 Defining characteristic: Integration of dozens of transistors on a
single silicon/germanium piece – “microchip” or “chip”
 Kibly started with germanium, Robert Noyce eventually used
silicon
 Led to the silicon chip => “Silicon Valley”
 Allowed dozens of transistors to exist on a single chip smaller
than a single discrete transistor
 Effect: Computers became faster, smaller & cheaper
 E.g. IBM System/360, DEC’s PDP-8 and PDP-11

27. 4th Generation: VLSI (1980 - )
 Defining characteristic: Integration of very large numbers of transistors on
a single chip
 3rd generation had only multiple transistors on a chip
 No. increased as manufacturing techniques improved: SSI (<100) => MSI
(<1000) => LSI (<10,000) => VLSI (>10,000)
 Led to the development of first microprocessor (4004) by Intel in 1971
 Effect: allowed computers to be cheaper, smaller & faster – led to
development of microprocessors
 Computers for consumers: Altair 8800 => Apple I & II => IBM’s PC

28. 5th Generation?
 Quantum computing
 Artificial Intelligence
 Massively parallel machines
 Non Von Neumann architectures

29. Common themes in evolution of
computers
 The same underlying fundamental concepts
 Obsession with
 Increase in performance
 Decrease in size
 Decrease in cost

30. Moore’s Law
 How small can we make transistors? How densely can we pack
them
 In 1965, Intel founder Gordon Moore stated “the density of
transistors in an integrated circuit will double every year” –
Moore’s Law
 Ended up being every after every 18 months
 Has hold up for almost 40 years
 However cannot hold forever – physical & financial limits
 Rock’s Law: “The cost of capital equipment to build
semiconductors will double every for years”

31. Moore’s Law

32. Moore’s Law
 Implications
 Cost of a chip remained almost unchanged
 Cost of components decreased
 Higher packing density, shorter electrical paths
 Higher speeds
 Smaller size
 Increased flexibility
 Reduced power & cooling requirements
 Fewer interconnections
 Increased reliability

33. Uniprocessor to Multiprocessor
 Because of physical limits – power limits
 Clock rates cannot increase forever
 Power = capacitive load x V^2 x frequency
 Multiple processors per chip – “cores”
 Programmers have to take advantage of multiple
processors
 Parallelism – similar to instruction level parallelism