1. E0001 Computers in Engineering1 The System Unit & Memory

2. E0001 Computers in Engineering2 Readings n “Computers in Your Future” - Chapter 2 n 1997 - chapter 2 n 1998 - 2A & 2B n “Using Computers A Gateway to Information” 1995 - Chapter 4 & 6 n 1997 - chapters 3 and 5 n 1999 - chapter 3

3. E0001 Computers in Engineering3 This Lecture: n the system unit n main memory - RAM, ROM n data representation - binary codes n error checking - Parity

4. E0001 Computers in Engineering4 The Binary System n Data, instructions are represented electronically with a binary or two-state numbering system. n three principal codes –ASCII –EBCDIC –Unicode

5. E0001 Computers in Engineering5 Binary Coding Schemes n ASCII –American Standard Code for Information Interchange –most widely used –8 bits = 1 byte n EBCDIC –Extended Binary Coded Decimal Interchange Code –industry standard for large computers n Unicode –sixteen bit code –designed to support languages like Chinese & Japanese

6. E0001 Computers in Engineering6 Error Checking n parity –odd –even n Find out the difference between odd and even parity! - Exam Hint!!!!!

7. E0001 Computers in Engineering7

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

9. E0001 Computers in Engineering9 The Motherboard n contains –CPU –some memory chips –expansion slots

10. E0001 Computers in Engineering10

11. E0001 Computers in Engineering11 The CPU - central processing unit n part of the computer that executes instructions n sometimes called processor n is on a single electronic component - microprocessor chip n has two components –the control unit –arithmetic logic unit - ALU

12. E0001 Computers in Engineering12 The Control Unit n tells the rest of the computer how to carry out the programs instructions n directs (controls) movement between memory and the ALU n controls signals between CPU and input/output devices n machine cycle - fetching, decoding, executing, storing

13. E0001 Computers in Engineering13 The Arithmetic Logic Unit n performs two operations –arithmetic –logic n arithmetic operations - fundamental math operations –additions, subtraction, multiplication, division n logic operations - consist of comparisons – =, – =,

14. E0001 Computers in Engineering14 Microprocessor Chips n CISC chips - complex instruction set computer –most widely used chip design - hence runs a large number of existing programs –e.g. Intels Pentium n RISC chips - reduced instruction set computer –design is simpler, faster, less costly –e.g. PowerPC, Alpha chip

15. E0001 Computers in Engineering15 Memory - RAM n temporarily holds data, program instructions, and information n also know as RAM, primary storage, internal storage, or main memory n RAM - Random Access Memory –volatile –destructive write process; nondestructive read –memory has four types

16. E0001 Computers in Engineering16 RAM n four types –conventional memory consists of the first 640K of RAMconsists of the first 640K of RAM used by DOS and application programsused by DOS and application programs –upper memory located between 640K and 1Mlocated between 640K and 1M used by DOS - info about hardware; also application programsused by DOS - info about hardware; also application programs

17. E0001 Computers in Engineering17 –extended memory directly accessible memory above 1Mdirectly accessible memory above 1M available on most microprocessorsavailable on most microprocessors not accessed by all programsnot accessed by all programs –expanded memory special ‘island’ of memory up to 32MB that exists outside the DOS 640K limitspecial ‘island’ of memory up to 32MB that exists outside the DOS 640K limit intended to help older micros that cannot directly access memory over 1Mintended to help older micros that cannot directly access memory over 1M n cache memory –high speed RAM –stores most frequently used instructions –sits between CPU and Main memory

18. E0001 Computers in Engineering18 cache memory

19. E0001 Computers in Engineering19 ROM n Read Only Memory n non-volatile n contents cannot be changed by the user n typically contain instructions for detailed computer operations e.g. start the computer, put characters on the screen, give keyboard keys special features n two types

20. E0001 Computers in Engineering20 ROM types n PROM - programmable read only memory –once programmed cannot be changed n 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. E0001 Computers in Engineering21 System Clock n controls the speed of operations with in the computer n expressed in MHz - mega hertz - one million cycles per second n faster clock speed - faster computer operates

22. E0001 Computers in Engineering22 Expansion Slots n memory expansion slots –several additional RAM chips increase the memory capacity n Network adaptor cards –used to connect the computer to one or more computers –forms a communication network n Small computer system interface - “scuzzy”cards n PC cards

23. E0001 Computers in Engineering23 bus lines

24. E0001 Computers in Engineering24 Bus Lines n connects parts of the CPU to each other n links CPU to important hardware n four principal bus lines –Industry Standard Architecture (ISA) –Micro Channel Architecture (MCA) –Extended Industry Standard Architecture (EISA) –Peripheral Connect Interconnect (PCI)

25. E0001 Computers in Engineering25 Ports n connecting socket on the outside of the system unit n parallel ports n serial ports