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Objectives Know the difference between computer organization and computer architecture. Understand units of measure common to computer systems. Appreciate the evolution of computers. Understand the computer as a layered system. Be able to explain the von Neumann architecture and the function of basi...

Objectives Know the difference between computer organization and computer architecture. Understand units of measure common to computer systems. Appreciate the evolution of computers. Understand the computer as a layered system. Be able to explain the von Neumann architecture and the function of basic computer components. 1 Weekly Learning Outcomes 1. Explain the organization of a computer 2. Understand the computer as a layered system. 3. Explain the von Neumann architecture 2 Overview (1 of 2) Why study computer organization and architecture? – Design better programs, including system software such as compilers, operating systems, and device drivers. – Optimize program behavior. – Evaluate (benchmark) computer system performance. – Understand time, space, and price tradeoffs. 3 Overview (2 of 2) 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 aspects of system implementation as seen by the programmer (e.g., instruction sets, instruction formats, data types, addressing modes). – How do I design a computer? 4 Computer Systems (1 of 2) There is no clear distinction between matters related to computer organization and matters relevant to computer architecture. 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. 5 Computer Systems (2 of 2) 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 transferring data to and from the outside world 6 An Example System (1 of 6) Consider this advertisement: 7 An Example System (2 of 6) Measures of capacity and speed: – – – – – – – – Kilo- (K) = 1 thousand = 103 and 210 Mega- (M) = 1 million = 106 and 220 Giga- (G) = 1 billion = 109 and 230 Tera- (T) = 1 trillion = 1012 and 240 Peta- (P) = 1 quadrillion = 1015 and 250 Exa- (E) = 1 quintillion = 1018 and 260 Zetta- (Z) = 1 sextillion = 1021 and 270 Yotta- (Y) = 1 septillion = 1024 and 280 Whether a metric refers to a power of ten or a power of two typically depends upon what is being measured. 8 An Example System (3 of 6) Hertz = clock cycles per second (frequency) – 1MHz = 1,000,000Hz – Processor speeds are measured in MHz or GHz. Byte = a unit of storage – – – – – 1KB = 210 = 1024 Bytes 1MB = 220 = 1,048,576 Bytes 1GB = 230 = 1,099,511,627,776 Bytes Main memory (RAM) is measured in GB. Disk storage is measured in GB for small systems, TB (240) for large systems. 9 An Example System (4 of 6) Measures of time and space: – – – – – – – – Milli- (m) = 1 thousandth = 10-3 Micro- () = 1 millionth = 10-6 Nano- (n) = 1 billionth = 10-9 Pico- (p) = 1 trillionth = 10-12 Femto- (f) = 1 quadrillionth = 10-15 Atto- (a) = 1 quintillionth = 10-18 Zepto- (z) = 1 sextillionth = 10-21 Yocto- (y) = 1 septillionth = 10-24 10 An Example System (5 of 6) Millisecond = 1 thousandth of a second – Hard disk drive access times are often 10 to 20 milliseconds. Nanosecond = 1 billionth of a second – Main memory access times are often 50 to 70 nanoseconds. Micron (micrometer) = 1 millionth of a meter – Circuits on computer chips are measured in microns. 11 An Example System (6 of 6) We note that cycle time is the reciprocal of clock frequency. A bus operating at 133MHz has a cycle time of 7.52 nanoseconds: 1/(133,000,000 cycles/second) = 7.52 ns/cycle Now back to the advertisement... 12 Historical Development (1 of 11) To fully appreciate the computers of today, it is helpful to understand how things got the way they are. The evolution of computing machinery has taken place over several centuries. In modern times computer evolution is usually classified into four generations according to the salient technology of the era. We note that many of the following dates are approximate. 13 Historical Development (2 of 11) Generation Zero: Mechanical Calculating Machines (1642–1945) – Calculating Clock: Wilhelm Schickard (1592–1635) – Pascaline: Blaise Pascal (1623–1662) – Difference Engine: Charles Babbage (1791–1871), also designed but never built the Analytical Engine. – Punched card tabulating machines: Herman Hollerith (1860–1929) Hollerith cards were commonly used for computer input well into the 1970s. 14 Historical Development (3 of 11) The First Generation: Vacuum Tube Computers (1945– 1953) – Atanasoff Berry Computer (1937–1938) solved systems of linear equations. – John Atanasoff and Clifford Berry of Iowa State University 15 Historical Development (4 of 11) The First Generation: Vacuum Tube Computers (1945–1953) – Electronic Numerical Integrator and Computer (ENIAC) – John Mauchly and J. Presper Eckert – University of Pennsylvania, 1946 The ENIAC was the first general-purpose computer. 16 Historical Development (5 of 11) The First Generation: Vacuum Tube Computers (1945–1953) – The IBM 650 first mass-produced computer (1955). It was phased out in 1969. – Other major computer manufacturers of this period include UNIVAC, Engineering Research Associates (ERA), and Computer Research Corporation (CRC). UNIVAC and ERA were bought by Remington Rand, the ancestor of the Unisys Corporation. CRC was bought by the Underwood (typewriter) Corporation, which left the computer business. 17 Historical Development (6 of 11) The Second Generation: Transistorized Computers (1954– 1965) – IBM 7094 (scientific) and 1401 (business) – Digital Equipment Corporation (DEC) PDP-1 – Univac 1100 – Control Data Corporation 1604 –... and many others. These systems had few architectural similarities. 18 Historical Development (7 of 11) The Third Generation: Integrated Circuit Computers (1965–1980) – – – – IBM 360 DEC PDP-8 and PDP-11 Cray-1 supercomputer... and many others. By this time, IBM had gained overwhelming dominance in the industry. – Computer manufacturers of this era were characterized as IBM and the BUNCH (Burroughs, Unisys, NCR, Control Data, and Honeywell). 19 Historical Development (8 of 11) The Fourth Generation: VLSI Computers (1980–????) – Very large scale integrated circuits (VLSI) have more than 10,000 components per chip. – Enabled the creation of microprocessors. – The first was the 4-bit Intel 4004. – Later versions, such as the 8080, 8086, and 8088 spawned the idea of “personal computing.” 20 Historical Development (9 of 11) Moore’s Law (1965) – Gordon Moore, Intel founder – “The density of transistors in an integrated circuit will double every year.” Contemporary version: – “The density of silicon chips doubles every 18 months.” But this “law” cannot hold forever... 21 Historical Development (10 of 11) Rock’s Law – Arthur Rock, Intel financier – “The cost of capital equipment to build semiconductors will double every 4 years.” – In 1968, a new chip plant cost about $12,000. – At the time, $12,000 would buy a nice home in the suburbs. – An executive earning $12,000 per year was “making a very comfortable living.” 22 Historical Development (11 of 11) Rock’s Law – In 2012, a chip plants under construction cost well over $5 billion. $5 billion is more than the gross domestic product of some small countries, including Barbados, Mauritania, and Rwanda. – For Moore’s Law to hold, Rock’s Law must fall, or vice versa. But no one can say which will give out first. 23 The Computer Level Hierarchy (1 of 7) Computers consist of many things besides chips. Before a computer can do anything worthwhile, it must also use software. Writing complex programs requires a “divide and conquer” approach, where each program module solves a smaller problem. Complex computer systems employ a similar technique through a series of virtual machine layers. 24 The Computer Level Hierarchy (2 of 7) 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. 25 The Computer Level Hierarchy (3 of 7) Level 6: The User Level – Program execution and user interface level – The level with which we are most familiar 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. 26 The Computer Level Hierarchy (4 of 7) 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. 27 The Computer Level Hierarchy (5 of 7) 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. 28 The Computer Level Hierarchy (6 of 7) 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 lowlevel language that is implemented by the hardware. – Hardwired control units consist of hardware that directly executes machine instructions. 29 The Computer Level Hierarchy (7 of 7) 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. 30 Cloud Computing: Computing as a Service (1 of 5) The ultimate aim of every computer system is to deliver functionality to its users. Computer users typically do not care about terabytes of storage and gigahertz of processor speed. Many companies outsource their data centers to third-party specialists, who agree to provide computing services for a fee. These arrangements are managed through service-level agreements (SLAs). 31 Cloud Computing: Computing as a Service (2 of 5) Rather than pay a third party to run a company-owned data center, another approach is to buy computing services from someone else’s data center and connect to it via the Internet. This is the idea behind a collection of service models known as Cloud computing. The “Cloud” is a visual metaphor traditionally used for the Internet. It is even more apt for service-defined computing. 32 Cloud Computing: Computing as a Service (3 of 5) The general term, Cloud computing, consists of several models: – Infrastructure as a Service (IaaS) provides only server hardware, secure network access to the servers, and backup and recovery services. The customer is responsible for all system software including the operating system and databases. Well-known IaaS platforms include Amazon EC2, Google Compute Engine, Microsoft Azure Services Platform, Rackspace, and HP Cloud. – Cloud storage is a limited type of IaaS that includes services such as Dropbox, Google Drive, and Amazon.com’s Cloud Drive. 33 Cloud Computing: Computing as a Service (4 of 5) More Cloud computing models: – Software as a Service, or SaaS. The consumer of this service buy application services Well-known examples include Gmail, Dropbox, GoToMeeting, and Netflix. – Platform as a Service, or PaaS. Provides server hardware, operating systems, database services, security components, and backup and recovery services. Well-known PaaS providers include Google App Engine and Microsoft Windows Azure Cloud Services. 34 Cloud Computing: Computing as a Service (5 of 5) Cloud computing relies on the concept of elasticity where resources can be added and removed as needed. You pay for only what you use. Virtualization is an enabler of elasticity. – Instead of having a physical machine, you have a “logical” machine that may span several physical machines, or occupy only part of a single physical machine. Potential issues: Privacy, security, having someone else in control of software and hardware you use 35 The von Neumann Model (1 of 7) Inventors of the ENIAC, John Mauchley and J. Presper Eckert, conceived of a computer that could store instructions in memory. The invention of this idea has since been ascribed to a mathematician, John von Neumann, who was a contemporary of Mauchley and Eckert. Stored-program computers have become known as von Neumann Architecture systems. 36 The von Neumann Model (2 of 7) Today’s stored-program computers have the following characteristics: – Three hardware systems: A central processing unit (CPU) A main memory system 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. 37 The von Neumann Model (3 of 7) This is a general depiction of a von Neumann system: These computers employ a fetch-decodeexecute cycle to run programs as follows... 38 The von Neumann Model (4 of 7) The control unit fetches the next instruction from memory using the program counter to determine where the instruction is located. 39 The von Neumann Model (5 of 7) The instruction is decoded into a language that the ALU can understand. 40 The von Neumann Model (6 of 7) Any data operands required to execute the instruction are fetched from memory and placed into registers within the CPU. 41 The von Neumann Model (7 of 7) The ALU executes the instruction and places results in registers or memory. 42 Conclusion 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 transferring data to and from the outside world The ultimate aim of every computer system is to deliver functionality to its users. The Von Neumann Systems employ a fetch-decode-execute cycle to run programs. 43