מבנה המחשב

1. מבנה המחשב • מועבר ע”י דניסיטרון • כל החומר על הקורס (החומר שיילמד, תרגילים, ציונים, שעות קבלה …) נמצא ב: http://shekel.jct.ac.il/~citron/ca • בהתאם לאמונה שלי שתלמיד שאינו שולט באנגלית לא יכול להתהדר בתואר אקדמי במדעי המחשב, אזי:זה השקף האחרון בעברית שתראו בקורס

2. The Course’s Goals • To be interesting and fun. A bored student won’t learn much. • To teach you things you don’t know yet. If you think a topic is interesting, I’ll try to include it in the course (will the Spurs repeat is interesting, but …) • And of course to give you an idea of what goes on under the covers of your PC, Workstation or Super-Computer.

3. General Information • Contact is by e-mail (citron@mail.jct.ac.il), phone (6751168 (jct), 6585766 (hu), 6786784 (home)),or in person (Thursdays, 18:45 - 19:45, room 210). • Grade: the final grade is composed of a final exam (70%) and three mini-exams (30%), out of which the 2 best will be used. • Assignments are optional. They will be given in the same format as the mini-exams.

4. Talking to the Computer • In order to “talk” to the computer we must send it electronic signals. The easiest signals for the machine to understand are on and off (in real life these signals are high voltage and low voltage). • Thus the computer’s alphabet is composed of two symbols 0 and 1. Any “words” composed with these 2 numbers are called binary numbers. • Computers are slaves to our commands and each individual command is called an instruction. • For instance the binary number 10001100100000 tells one computer to add 2 numbers.

5. Assembly Language • The first programmers (back in the late 40s) spoke to computers using binary numbers. • This,of course, was very tiring. So written codes for the instructions were created. At first they were converted into binary by hand. • But very soon a program was written that converted these symbols to binary. This program was called an assembler. • Thus the symbolic names of the instructions are called the assembly language.

6. High Level Languages • While writing in assembly code is much more productive than writing in binary it is still unnatural. Each machine instruction must be written on a single line, forcing the programmer to think like a machine. • So if it is possible to translate assembly language to binary, what prevents us from writing in some higher level? • The answer was: nothing. Although more complex than the assembler this program called the compiler translated high-level languages (like C++) to assembler.

7. A Simple Example • The high level expression in C++:A + B • Will be translated to the assembly statement:add A,B • The assembler will then translate it into the binary instruction:1000110010100000

8. Another Example

9. Compiling and Linking a Program User code compile link hello.cpp hello.obj hello.exe link I/O libraryio.lib

10. OK, but how does it work? • So we have a file which contains binary code (this file is called an executable file). What does the computer do with it? • We will explain the details in future lessons but in a nutshell (על רגל אחת)the file is loaded from the hard disk into memory (by, how obvious, the loader), the processor reads the instructions one by one and executes them. • With the use of a simple disassembler hackers, virus writers, virus busters and even you can read the binary code.

11. The 5 Classic Components Data flows from the input devices into memory, from the memory into the processor. The data is then processed and written back to memory. It is then stored or displayed in the output devices. Computer Processor Memory Devices Control Input Datapath Output

12. The Processor The “heart” (and brain) of the computer. Schedules instruction execution (the Control) and executes the instructions (the Datapath). This schematic layout is of the intel Pentium processor.

13. Photos of Dies MIPS R10000 Intel Pentium

14. Modern Microprocessors The major microprocessor manufacturers and their products are: • Intel - Pentium, Pentium Pro, Pentium II/III, Itanium (Merced) to be released in mid 2000. • Compaq (formerly Digital) - Alpha 21064, 21164, 21264, 21364. • Silicon Graphics - MIPS R4400, R5000, R8000, R10000, R120000 • Motorola, Apple, IBM - PowerPC 601, 603, 604, 604e, 740, 750 • HP - PA-7100, 7200, 8000, 8200, 8500 • Sun - Sparc, SuperSparc, HyperSparc, UltraSparc I/II/III

15. Performance Increase The rate of performance improvement doubles every 1.6 years, or 1.54 per year. The following graph shows the improvement of workstations over a period of 10 years.

16. Most Popular Microprocessor Families* • 80x86 50,000,000 • MIPS 5,500,000 • PowerPC 3,300,000 • SPARC 700,000 • HP PA-RISC 300,000 • DEC Alpha 200,000 * The numbers are for 1996

17. Memory The motherboard contains the memory of the computer in addition to the connections between the I/O devices and the memory/processor. The memory which is also called DRAM (Dynamic Random Access Memory) is installed in slots called SIMM (Single Inline Memory Modules) slots. The memory is “blood system” of the computer. All data flows through it from the devices to the processor.

18. Motherboard Photo

19. Memory Capacity Growth Memory capacity has quadrupled (גדל פי 4 ) every 3 years. The following chart shows how SIMMs have grown over a period of 20 years.

20. I/O Devices I/O devices can be divided into 3: • Input - keyboard, mouse, joystick, scanner, CDROM, microphone, digital camera ... • Output - printer, display, barcode projector, speakers ... • Input/Output - hard disks, floppy disks, magnetic tapes, VR (Virtual reality) helmets and gloves …

21. Volatile and Nonvolatile Memory • Loss of power in the computer will cause the data in memory to be erased. Memory that “forgets” its contents is called volatile. • In contrast a video tape doesn’t lose its contents when the VCR is disconnected. This is because the tape is magnetic, thus it is a nonvolatile memory technology. • It is obvious that we will use nonvolatile technologies for storage devices, to store programs and data between runs.

22. Storage Devices • The volatile memory which holds the program while it is running is called the main or primary memory. • The nonvolatile memory used to store the programs between runs is called secondary memory. • All types of disks (hard, floppy, Zip, Jaz, optical, CDROM, CDRAM) and tapes are nonvolatile. • So why use volatile memory at all?

23. Memory Access Times & Size • Volatile memory is much faster. The access time of DRAM is between 50-100 nanoseconds. • Hard disk access times are between 5-20 milliseconds. Making DRAM about 100,000 times faster. • So why don’t we use volatile hard disks?Cost. A megabyte of disk is 50 times cheaper than a megabyte of DRAM (and of course electric current will have to be maintained). • DRAM sizes for desktop systems are 64 -256 MB. • Hard disk sizes are 4 - 8 GB.

24. The Graphic Display • Based on television technology the CRT (raster cathode ray tube) Display scans an image one line at a time 50-120 times a second. At this refresh rate people don’t notice the flicker of the screen. • The image is composed of a matrix of picture elements, or pixels, which can be represented as a matrix of bits called a bit map. This image resides on the graphic card which is the interface between processor and memory to the display. • Depending on the screen size and resolutionthe matrix size ranges from 512x340 to 1560x1280 pixels, common size are 800x600, 1024x768, and 1280x1024.

25. Color and Size • A display that has 1 bit per pixel will be a a black and white display. • A gray-scale display supports 256 different shades of black and white. 8 bits per pixel are required. • There are colored displays with 8, 16 and 24 (true color) bits per pixel. Thus a graphic card with 1 MB of memory can contain a matrix of 1024x768 8 bit pixels, or a matrix of 800x600 16 bit pixels. • Screen sizes range from 14” (old), 15” (still common unfortunately), 17” (not bad) to 19” and 21” (need a flat screen already).

26. A Graphic Display (no pun intended) A beam is shot through vacuum onto the screen, the pixel value changes the voltage of the beam which draws a different color.

27. Computer Networks • The item that is missing from the 5 classic components is networking. It can’t be covered under any of the other components. • And yet no computer is complete without it. • Networking supplies: • Communication: Information exchange between computers. • Resource sharing: Computers can share I/O devices. • Nonlocal access: Users don’t have to be physically near the computer they are using.