Lecture #12

1. IT-101Section 001 Introduction to Information Technology Lecture #12

2. Overview From Notes… • Computer Development • Computer architecture

3. Introduction • Computer is arguably the most important tool in the areas of engineering, science, business etc. etc. • Data acquisition and analysis • Simulation • Embedded applications • Process control • Condition monitoring and fault diagnosis systems • Automatic testing equipment • Robotics • Telecommunications • Productivity software (word processing, spreadsheets, databases, presentation) etc……………

4. Computer development • The Abacus- Babylonia-4th century B.C. • The Difference Engine- Charles Babbage 1822 • Vacuum tube - John Ambrose Fleming 1904 • The ENIAC (Electronic Numerical Integrator and Computer)-1945 • Used 17,478 vacuum tubes • Too late for WW-II, but was used in the cold war to perform calculations to build a hydrogen bomb

5. City of Philadelphia reportedly experienced brown-outs when ENIAC drew power at its home at the the University of Pennsylvania (http://www.pbs.org/wgbh/aso/databank/entries/dt45en.html) • Was not a general purpose computer: programming meant rewiring with punch cards and switches • One of ENIAC's greatest feats was in showing the potential of what could be accomplished in the future • Transistor - Nobel prize in physics in 1956

6. Integrated Circuit (chip) - Jack Kilby 1958 (Nobel prize in physics in 2000) • First commercially available IC’s developed by Texas Instruments and Fairchild semiconductor corp. • Generations of IC’s: • Small scale integration - 1965 • 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 Apple I computer (1976)

7. Moore’s Law: Number of transistors on a chip will double every 18 months.

8. Computer Architecture Central Processing Unit Main Memory Systems Interconnection Input Output

9. Components of a Computer System Storage (External memory) input/output central processing unit Main Memory (Internal memory)

10. Component description • Central Processing Unit (CPU) or microprocessor, controls the operation of the computer and performs its data processing functions • Main memory - also called internal memory stores instructions and data. Memory is partitioned into separate instruction and data spaces • Input/output (I/O) – moves data between the computer and its external environment • System interconnection – some mechanism that provides for communications among the CPU, the main memory, and the I/O devices

11. Structure of the CPU storage memory input/output control unit ALU registers registers cache memory flags

12. Components of the CPU • Arithmetic and Logic Unit (ALU): processes the data in the registers according to instructions issued by the control unit. Performs arithmetic (addition, subtraction, etc..) and logical (comparison) operations • Registers: provides temporary storage for data and instructions. It handles instructions and data at 10 times the speed of cache memory. Registers facilitate the movement of data and instructions between RAM, the control unit and the ALU • Control unit registers: • The instruction register contains the current instruction being executed • The program register (instruction pointer) contains the RAM address of the next instruction to be executed • ALU registers • The accumulator register stores the result of ALU operations

13. Internal CPU interconnection: some mechanism that provides for communication among the control unit, ALU, and registers • Control Unit: controls the operation of the CPU and hence the computer. Interprets instructions, moves data to/from memory and registers, instructs ALU to perform certain operations, increments instruction pointer, etc. During program execution, instructions in a program are moved from the RAM into the control unit, where it is decoded and interpreted by the decoder • Flags: 1-bit memory, or 1-bit registers and hold information on what has recently happened in the CPU. These are set to 1 or 0 depending on the results of internal operations such as results of ALU operations (zero or negative result) or external operations such as interrupts (commands that tell the processor to stop execution and wait for further instruction)

14. Cache Memory: Small fast memory that improves CPU’s efficiency. Increases computer throughput, and is a high-speed holding area for program instructions and data. It holds only instructions and data that are likely to be needed by the CPU. While programs are running on the computer, the same data or instructions might be needed frequently. In such cases, the processor first checks the cache memory for the data or instructions, thereby reducing the need for frequent access to the RAM and speeding up the processing

15. Microprocessor System Buses RAM ROM Control Bus Microprocessor (CPU) Data Bus Input/Output (I/O) Address Bus

16. System Buses • A BUSis an internal communications path consisting of a number of lines connecting the system components • Control bus –The control bus synchronizes system events like memory access, system interrupts, I/O, etc. • Address bus – Source and destination addresses are sent over the address bus to identify a particular location in memory or input/output port. In other words, it serves as the computer’s “post office” • Data bus – two way path for transferring data and instructions in and out of the microprocessor

17. Main (Internal) Memory • RAM – Random Access Memory. Temporary read/write memory. Applications are typically loaded into RAM during computer use. Types of RAM include: • SRAM (static) , DRAM (dynamic ), EDO RAM (extended data out) , SDRAM (synchronous dynamic-most new PC’s are equipped with this RAM which is able to synchronize itself with the processor, enabling data transfer at more than twice the speed of previous RAM technologies) • SRAM is called static because the memory retains its contents as long as power is supplied-It does not have to be periodically refreshed as in DRAM. It is faster than DRAM (The contents of the memory can be read much faster), however is more expensive and is larger in size • DRAM is called Dynamic RAM because the memory content needs to be refreshed periodically (every few milliseconds) due to leakage of electrical charge. It is slower than SRAM, but cheaper and smaller in size

18. ROM – Read Only Memory. ROM can typically be written once, but read many times. It is used to store BIOS (Basic Input/Output System-helps to load and locate an operating system), external to microprocessor, and computer instruction sets, internal to microprocessor • The contents of the ROM are hard wired by the manufacturer in a typical ROM chip. When you turn the computer on, ROM automatically prepares the computer system and loads the initial display screen prompt • A variation of ROM is PROM (Programmable Read Only Memory), in which the user can load programs and data that are read only. This can be done with device called a PROM programmer. Writing to a PROM destroys the internal links, so a basic PROM can only be programmed once

19. EPROMs (Erasable Programmable Read Only Memory) is a variation of PROM, and is rewritable. It can be erased by exposing the chip to ultraviolet light. It can then be programmed with an EPROM programmer • Flash memory is a type of PROM that can be easily altered by the user. They are also called EEPROMs (Electrically Erasable Read Only Memory) because they can be electrically erased then written on to (flashed) without having to take them out of the computer, and without using ultraviolet light. • Since RAM can be read faster than most ROMs, the frequently used content of the ROM is sometimes copied to RAM (shadowed)

20. Storage (External Memory) • Magnetic disk • Hard disk • Floppy disks • Zip disks • Optical media • CD-ROM • DVD • Magneto-optical disks (Pinnacle drives) • Magnetic tape (used primarily for long term archive)

21. Some Input Devices • Keyboard • Keypad • Mouse • Voice activation • Touch screen • Digitizers and pen-based (stylus) systems • Switches

22. Some Output Devices • Monitor • Printer • Speakers • Communication (comm) ports • Modems (both input and output) • Network interface cards (both input and output) • Motors