E0001 Computers in Engineering

1. E0001 Computers in Engineering The System Unit & Memory

2. Readings • “Computers in Your Future” - Chapter 2 • 1997 - chapter 2 • 1998 - 2A & 2B • “Using Computers A Gateway to Information” 1995 - Chapter 4 & 6 • 1997 - chapters 3 and 5 • 1999 - chapter 3

3. This Lecture: • the system unit • main memory - RAM, ROM • data representation - binary codes • error checking - Parity

4. The Binary System • Data, instructions are represented electronically with a binary or two-state numbering system. • three principal codes • ASCII • EBCDIC • Unicode

5. Binary Coding Schemes • ASCII • American Standard Code for Information Interchange • most widely used • 8 bits = 1 byte • EBCDIC • Extended Binary Coded Decimal Interchange Code • industry standard for large computers • Unicode • sixteen bit code • designed to support languages like Chinese & Japanese

6. Error Checking • parity • odd • even • Find out the difference between odd and even parity! - Exam Hint!!!!!

8. The System Unit • connected to input and output devices, and secondary storage contains:- • motherboard • central processing unit - CPU • main memory • system clock • expansion slots and boards • bus lines • ports

9. The Motherboard • contains • CPU • some memory chips • expansion slots

11. The CPU - central processing unit • part of the computer that executes instructions • sometimes called processor • is on a single electronic component - microprocessor chip • has two components • the control unit • arithmetic logic unit - ALU

12. The Control Unit • tells the rest of the computer how to carry out the programs instructions • directs (controls) movement between memory and the ALU • controls signals between CPU and input/output devices • machine cycle - fetching, decoding, executing, storing

13. The Arithmetic Logic Unit • performs two operations • arithmetic • logic • arithmetic operations - fundamental math operations • additions, subtraction, multiplication, division • logic operations - consist of comparisons • =, <, >

14. Microprocessor Chips • CISC chips - complex instruction set computer • most widely used chip design - hence runs a large number of existing programs • e.g. Intels Pentium • RISC chips - reduced instruction set computer • design is simpler, faster, less costly • e.g. PowerPC, Alpha chip

15. Memory - RAM • temporarily holds data, program instructions, and information • also know as RAM, primary storage, internal storage, or main memory • RAM - Random Access Memory • volatile • destructive write process; nondestructive read • memory has four types

16. RAM • four types • conventional memory • consists of the first 640K of RAM • used by DOS and application programs • upper memory • located between 640K and 1M • used by DOS - info about hardware; also application programs

17. extended memory • directly accessible memory above 1M • available on most microprocessors • not accessed by all programs • expanded memory • special ‘island’ of memory up to 32MB that exists outside the DOS 640K limit • intended to help older micros that cannot directly access memory over 1M • cache memory • high speed RAM • stores most frequently used instructions • sits between CPU and Main memory

18. cache memory

19. ROM • Read Only Memory • non-volatile • contents cannot be changed by the user • typically contain instructions for detailed computer operations e.g. start the computer, put characters on the screen, give keyboard keys special features • two types

20. ROM types • PROM - programmable read only memory • once programmed cannot be changed • EPROM - erasable programmable read only memory • PROM chip that can be erased by UV light • new instructions can then be written • EEPROM - electrically erasable

21. System Clock • controls the speed of operations with in the computer • expressed in MHz - mega hertz - one million cycles per second • faster clock speed - faster computer operates

22. Expansion Slots • memory expansion slots • several additional RAM chips increase the memory capacity • Network adaptor cards • used to connect the computer to one or more computers • forms a communication network • Small computer system interface - “scuzzy”cards • PC cards

23. bus lines

24. Bus Lines • connects parts of the CPU to each other • links CPU to important hardware • four principal bus lines • Industry Standard Architecture (ISA) • Micro Channel Architecture (MCA) • Extended Industry Standard Architecture (EISA) • Peripheral Connect Interconnect (PCI)

25. Ports • connecting socket on the outside of the system unit • parallel ports • serial ports