Lecture 2 Last Lecture Computer Organization vs Computer

Lecture 2 • Last Lecture – – – Computer Organization vs. Computer Architecture Principle of equivalence of hardware and software Computer Evolution Moore’s Law vs. Rock’s Law Main Components of a Computer Measures of Capacity, Speed, Time, Space • Today’s Lecture – The Computer Level Hierarchy – The Von Neumann Model – Non-Von Neumann Model 1

Computer Organization vs. Architecture • Computer organization – Encompasses all physical aspects of computer systems. – E. g. , circuit design, control signals, memory types. – How does a computer work? • Computer architecture – Logical and abstract of system implementation as seen by the programmer. – E. g. , instruction sets, instruction formats, data types, addressing modes, memory access methods, and I/O mechanisms. – How do I design a computer? • Principle of Equivalence of Hardware and Software: – Any task done by software can also be done using hardware, and any operation performed directly by hardware can be done using software. * * Assuming speed is not a concern. 2

Computer Evolution • Generation Zero: Mechanical Calculating Machines – Calculating Clock : First mechanical calculator, add and subtract numbers with as many as six digits. – Pascaline : Addition with carry and subtraction. – Difference Engine & Analytical Engine - Charles Babbage • Based on a calculating technique called the method of difference • The Analytical Engine included several components associated with modern computers: an arithmetic processing unit to perform calculations, a memory, and input and output devices. • “the father of computing” – Punched card tabulating machines: data input • Electronics technology continues to evolve – Increased capacity and performance – Reduced cost 3

Computer Evolution • The first completely electronic computer, ABC solved systems of linear equations • ENIAC was the first all-electronic, general-purpose digital computer. Year Technology Relative performance/cost 1951 Vacuum tube 1965 Transistor 1975 Integrated circuit (IC) 1995 Very large-scale Integrated Circuit 2, 400, 000 2013 Ultra large-scale Integrated Circuit 250, 000, 000 1 35 900 4

Moore’s Law vs. Rock’s Law • Moore’s law: The transistor density of semiconductor chips would double roughly every 18 months. • Rock’s law: The cost of capital equipment to build semiconductors will double every four years. • Rock's law can be seen as the economic flip side to Moore’s Law. • For Moore’s Law to hold, Rock’s Law must fall, or vice versa. But no one can say which will give out first. 5

Computer Components • At the most basic level, a computer is a device consisting of three pieces: – A processor to interpret and execute programs – A memory to store both data and programs – A mechanism for data input and output 6

Measures of Capacity and Speed • Typical measures of capacity: KB, MB, GB, TB • Typical measures of speed: kb/s, Mb/s, Gb/s, MHz, GHz Prefix Symbol Power of 10 Power of 2 Kilo K 1 thousand = 103 210=1024 Mega M 1 million = 106 220 Giga G 1 billion = 109 230 Tera T 1 trillion= 1012 240 Peta P 1 quadrillion = 1015 250 Exa E 1 quintillion = 1018 260 Zetta Z 1 sexitillion = 1021 270 Yotta Y 1 septillion = 1024 280 Whether a metric refers to a power of 10 or a power of 2 typically depends upon what is being measured. 7

Measures of Time and Space • Prefix Symbol Power of 10 Power of 2 Milli 1 thousandth = 10 -3 2 -10 Micro 1 millionth = 10 -6 2 -20 Nano 1 billionth = 10 -9 2 -30 Pico 1 trillionth= 10 -12 2 -40 Femto 1 quadrillionth = 10 -15 2 -50 Atto 1 quintillionth = 10 -18 2 -60 Zepto 1 sexitillionth = 10 -21 2 -70 Yocto 1 septillionth = 10 -24 2 -80 Generally, negative powers refer to powers of 10, not powers of 2. 8

Exercises Solution a) b) c) d) e) f) g) h) i) j) 1 second = 1000 milliseconds 1 second = 1, 000 microseconds 1 millisecond = 1, 000 nanoseconds 1 milliseconds = 1, 000 microseconds 1 microseconds = 1, 000 nanoseconds 1 GB = 1, 000 (or 230/210=220) KBs 1 MB = 1, 000 (or 220/210=210) KBs 1 GB = 1, 000 (or 230/220=210) MBs 20 MBs = 20, 000 or (or 20 * 220) Bytes 2 GBs = 2, 000(or 231/210=221) KBs 9

Lecture 2 • Last Lecture – – – Computer Organization vs. Computer Architecture Principle of equivalence of hardware and software Computer Evolution Moore’s Law vs. Rock’s Law Main Components of a Computer Measures of Capacity, Speed, Time, Space • Today’s Lecture – The Computer Level Hierarchy – The Von Neumann Model – Non-Von Neumann Model 10

Divide and Conquer • • Divide a problem into modules. Design each module separately. Each module performs a specific task Modules need only know how to interface with other modules to make use of them. • Computer system organization can be approached in a similar manner? – Abstraction: • • The machine is built from a hierarchy of levels, Each level has a specific function, Each level exists as a distinct hypothetical machine, also called virtual machine. Each level’s virtual machine executes its own particular set of instructions, calling upon machines at lower levels to carry out the tasks when necessary. 11

1. 6 The Computer Level Hierarchy • Each virtual machine layer is an abstraction of the level below it. • The machines at each level execute their own particular instructions, calling upon machines at lower levels to perform tasks as required. • Computer circuits ultimately carry out the work. 12

The Computer Level Hierarchy • Level 6: The User Level – Program execution and user interface level. – The level with which we are most familiar. – Executable programs • Level 5: High-Level Language Level – The level with which we interact when we write programs in languages such as C, Pascal, Lisp, and Java. 13

The Computer Level Hierarchy • Level 4: Assembly Language Level – Acts upon assembly language produced from Level 5, as well as instructions programmed directly at this level. • Level 3: System Software Level – Controls executing processes on the system. – Protects system resources. – Assembly language instructions often pass through Level 3 without modification. 14

1. 6 The Computer Level Hierarchy • Level 2: Machine Level – Also known as the Instruction Set Architecture (ISA) Level. – Consists of instructions that are particular to the architecture of the machine. – Programs written in machine language need no compilers, interpreters, or assemblers. 15

1. 6 The Computer Level Hierarchy • Level 1: Control Level – A control unit decodes and executes instructions and moves data through the system. – Control units can be microprogrammed or hardwired. • A microprogram is a program written in a low-level language that is implemented by the hardware. • Hardwired control units consist of hardware that directly executes machine instructions. 16

1. 6 The Computer Level Hierarchy • Level 0: Digital Logic Level – This level is where we find digital circuits (the chips). – Digital circuits consist of gates and wires. – These components implement the mathematical logic of all other levels. 17

The Stored Program Computer • 1943: ENIAC – Inventor: John Mauchly and J. Presper Echert. – The first all-electronic, general-purpose digital computer. – 18, 000 tubes – Memory: 20 10 -digit numbers (decimal) – Hard-wired program -- settings of dials, switches and cables. – Completed in 1946. • 1944: Beginnings of EDVAC(Electronic Discrete Variable Automatic Computer) – Program stored in memory – Binary operation – Not published due to World War II. – Completed in 1952 18 A poster showing a photograph of the army's ENIAC computer.

The von Neumann Model • 1945: John von Neumann – Wrote a report on the stored program concept, known as the First Draft of a Report on EDVAC • The basic structure proposed in the draft became known as the “von Neumann machine” (or model). – a memory, containing instructions and data – a processing unit, for performing arithmetic and logical operations – a control unit, for interpreting instructions 19

The von Neumann Model • Today’s stored-program machine architecture: – Three hardware systems: • A central processing unit (CPU) with a control unit, an arithmetic logic unit (ALU), registers (small storage areas) • A main memory system – Holds the programs that control the computer’s operation • An I/O system – The capacity to carry out sequential instruction processing. – A single data path between the CPU and main memory. • This single path is known as the von Neumann bottleneck. 20

The von Neumann Model • A general depiction of a von Neumann system. • Employ a fetchdecode-execute cycle to run programs 21

Instruction Processing: FETCH • The control unit fetches the next instruction from memory using the program counter to determine where the instruction is located. 22

Instruction Processing: DECODE • The instruction is decoded into a language that the ALU can understand. 23

Instruction Processing: FETCH OPERANDS • Any data operands required to execute the instruction are fetched from memory and placed into registers within the CPU. 24

Instruction Processing: EXECUTE • The ALU executes the instruction and places results in registers or memory. 25

Fetch-Decode-Execute cycle Fetch instruction from memory Decode instruction Evaluate address Fetch operands from memory Execute operation Store result 26

System Bus Model: Extension to von Neumann Architecture • von Neumann bottleneck: A single data path between the CPU and main memory. – Data bus: moving data between the main memory and the CPU registers. – Address bus: holds the address of the data that the data bus is currently accessing. – Control bus: carries the necessary control signals that specify how the information transfer is to take place. The Modified von Neumann Architecture, Adding a System Bus. 27

Today’s von Neumann Model • Programs and data – stored in a slow-to-access storage medium, such as a hard disk. – Copied to a fast-access, volatile storage medium such as RAM prior to execution. 28

Non-von Neumann Models • Improvements to conventional stored-program computers – adding specialized buses, floating-point units, and cache memories. • But enormous improvements in computational power require departure from the classic von Neumann architecture. • Parallel processing refers to a collection of different architectures: – Multiple separate computers working together – Multiple processors sharing memory – Multiple cores integrated onto the same chip • Cooperating von Neumann machines: parallel processing computers 29

Standards Organizations • The Institute of Electrical and Electronic Engineers (IEEE) – Promotes the interests of the worldwide electrical engineering community. – Establishes standards for computer components, data representation, and signaling protocols, among many other things. • The International Telecommunications Union (ITU) – Concerns itself with the interoperability of telecommunications systems, including data communications and telephony. 30

Standards Organizations • National groups establish standards within their respective countries: – The American National Standards Institute (ANSI) – The British Standards Institution (BSI) • The International Organization for Standardization (ISO) – Establishes worldwide standards for everything from screw threads to photographic film. – Is influential in formulating standards for computer hardware and software, including their methods of manufacture. 31