1. CSC 110 – Intro to Computing Lecture 8: Computing Components

2. Announcements Course slides are available from web page  Posted both before and after class  Slides after class includes my drawings Homework #2 due by 5PM today  Solution will be posted tonight  Quiz #2 will be on Tuesday CSC tutors are still available  Hours posted outside Wehle 206 & 208

3. Service Learning Reminder Get your site selection site form in to me last week (or as soon as possible) Remember to write an experience page each time you volunteer  Web page documenting what you did, what you learned, how you felt  Should help you write end report First set of experience pages due Feb. 23

4. There’s Something About Adders… Understand what these circuits do:  Half-adder add two bits  Full-adder adds two bits and any carry from the previous digit Know when to use each of the circuits:  Half-adder adds rightmost (least significant) bit  Full-adder adds all other bits, since a 1 may be carried into it

5. There’s Something About Adders… Be able to combine circuits to add multi- digit binary numbers:  Use carry-out from one adder as the carry-in for the next adder  Use half-adder to add least significant bit; full- adder everywhere else Do NOT memorize the gates in each  I will not ask you to draw this from memory  If you need it after this course, you can always look it up

6. Half-Adders Adds two input bits  Outputs result bit and carry bit  Cannot be used if there could be a carry-in bit So used to add least significant (rightmost) bit Very important circuit in computers  Addition is very common  Half-adder is found in every computer, calculator, digital watch…

7. Half-Adder Only this circuit is a Half-Adder  Other circuits may be equivalent, however Result Carry

8. Half-Adder How to know a circuit is equivalent to half- adder  Circuit is equivalent to a half-adder if both truth tables have identical output  Equivalence can be found in two ways: Memorizing the half-adder circuit and its truth table Memorizing the half-adder circuit and its truth table  Checking that the output matches the result of adding the input together 

9. Full-Adders Full-adder adds two input bits and the carry bit from the previous  Outputs result bit and another carry bit Needed to add all but least significant bit  Do not know when designing a processor everyplace we will ever carry a 1

10. Full-Adder More complex than a half-adder because we need to include the carry bit Result

11. How Does a Computer Work? Discussions usually begin with processor  More formally called the CPU or Central Processing Unit  Examples include: Pentium IV, PowerPC, Itanium, Pentium M…

12. CPU Design Processor includes many parts  Calculate mathematical & logical functions  Direct actions in rest of computer  Storing small amount of VERY fast memory

13. How a Computer Is Organized

14. Connecting the Computer

15. Arithmetic/Logical Unit Calculates mathematical & logical actions  Adds, subtracts, multiplies, divides, ANDs, ORs, NOTs, NORs… Uses only simply instructions which take one or two inputs a + b/c is two instructions: division and addition  Uses “registers”: VERY fast memory Run at speed of processor Only 16 - 64 registers available on a machine

16. “Input Units” Input Unit A device through which data and programs from the outside world are entered into the computer

17. “Output Units” Output unit A device through which results stored in the computer memory are made available to the outside world

18. Storage Devices Still need someway of remembering information  Secondary storage devices used to read/write information

19. Memory Hierarchy Time required changes depending on where you access memory  Registers: Drive 1 mile  RAM: Drive to Detroit (214 miles)  Hard Drive: Drive to Moon and back (twice!)  CD Rom: Drive to Sun and back Where something stored has slight impact

20. What’s New in Processors Lots of really interesting work going on  Have names like “Dynamic Branch Prediction” or “Register Renaming Windows”  Actually much more interesting than it sounds First ongoing revolution we will discuss  Most processors are 32-bit, …  … but newest processors are 64-bit

21. Why Bits Matter 1 bit captures 2 states: 0 or 1 2 bits captures 4 states: 00, 01, 10, 11 3 bits capture 8 states: 000, 001, 010, 011, 100, 101, 110, 111 4 bits captures 16 states: 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111

22. Binary Representation Each time we add a bit, we increase the number of states by a multiple of ____ How many different states can n bits represent? This is important because more states means more colors, more pixels, ability to process more money…

23. Sizes in Perspective 8 bits = 1 byte  4 bits = 1 nibble 1 GB = 1,073,741,824 bytes 1 TB = 1,099,511,627,776 bytes Federal debt (as of Feb. 3 rd ) $8,195,544,127,376.07 Largest database 549,755,813,888,000 bytes 1 PB = 1,125,899,906,842,624 bytes

24. Hard Drive Sizes in Perspective Problem with simplicity: MARKETING  Normally sizes are powers-of-two, but…  Hard drives sizes measured in powers-of-ten SizeActual SizeHard Drive Size 1 KB1024 bytes 1 MB1,048,576 bytes1,000,000 bytes 1 GB1,073,741,824 bytes1,000,000,000 bytes 60 GB64,424,509,440 bytes60,000,000,000 bytes 400 GB429,496,729,600 bytes400,000,000,000 bytes

25. Control Unit Organizes and directs program execution  Uses several special registers: Instruction Register (IR) holds instruction to execute Program Counter (PC) states instruction to execute next  Control unit insures program executes step- by-step in logical, orderly manner Often to the chagrin of people writing and using the program

26. von Neumann Architecture Prevalent in all computers today  Store data and instructions together  Uses control unit to drive entire machine  Assumes existence of input & output devices

27. von Neumann Computer Connections

28. Harvard Architecture Early “competitor” to von Neumann’s idea  Keep data and instructions in completely different areas  Uses separate controllers to handle programs (instructions) and everything else  Now used only in DSPs and other specialized data-intensive systems

29. Harvard Computer Connections Program Data

30. Memory Modern desktop machines are 32-bit  Means they access memory 32-bits at a time  How computers view memory contents:

31. Memory What does the data represent?  Could be a program, picture, mp3, CSC110 grades, …  Processor translates this data into something more meaningful  Output units then present this information

32. For next lecture Study for the quiz! Finish reading Section 5 Be ready to finish discussing:  Computer components