EGR 199:
Fundamentals of Engineering

What is Inside a PC?
09/20/99 Prabhaker Mateti
I think there is a world market for maybe five computers. - Thomas Watson, 1943, Chairman, IBM. There is no need for any individual to have a computer in their home. - Ken Olson, 1977, President, Chairman and Founder, Digital Equipment.

Table of Contents

Executive Summary
Educational Objectives

Pre-Lab


Suggested Preparations
Background Information
Procedures

Assembling the PC
Precautions
Power On Self Test
Booting from Floppy Disk
Booting from Floppy into DOS
Booting from Floppy into Linux
Booting from Windows 3.1 Hard Disk
Booting from Linux Hard Disk
Concluding Activities
Appendix A: Acronyms
Appendix B: Further Reading Links
Appendix C: Dave Barry
Achievement Test

Notes to TAs

Executive Summary

PCs have become a commodity item. Hundreds of thousands of households already have a LAN at home of two or three PCs. This lab makes the internals, both hardware and software, of a PC less mysterious. It aims to give the student the needed confidence to be able to build a PC at home. It also gives the installation experience of Linux, an operating system that is growing in popularity.

 

Educational Objectives

After performing this experiment, students should be able to:

  1. Recognize and understand the functionality of all hardware components of a PC: motherboard, disk drives, keyboard, mouse, monitor, and power supply.
  2. Understand the architecture of a PC: CPU, ROM, RAM, video controller, io ports, busses.
  3. Understand the role of software: BIOS, OS, and applications.

Suggested Preparation

Prior to performing the experiments of this Lab,  visit the sites listed in Appendix B: Further Reading Links and explore.

Background Information

Please refer to the Appendix A if you would like to find out what an acronym used below stands for.

Motherboards

The mother board holds all the other boards, the CPU, and the memory.  The other boards go into ISA, PCI, or AGP bus slots.

A typical Pentium motherboard is shown here. At the top-left is the power connector (white rectangle). There are three DIMM slots (with white "tips" at both ends) for memory at the top. Below these and adjacent to the power connector are the floppy and hard disk connectors. There are four PCI slots (white), two 16-bit ISA slots (black, at the bottom). Just above the PCI slots is the AGP slot (brown). The board has a socket-7 (white, bottom right) for the CPU.


CPU

In the PC world, the reigning CPU in 1998 is the Intel Pentium II. Pentium III was released in 1999. These are assembled on a small printed circuit board along with 512KB of L2 cache memory, and packaged in a black plastic case.

The K6-2 and K6-3 CPUs made by AMD have the form factor of the Pentium CPUs but are comparable to the Pentium IIs in performance.
Cyrix M2 CPU
Pentium CPU
AMD K6-2 CPU
Pentium-II CPU
In the Benchmark results shown here, the "current processor" was a IBM/Cyrix 6x86-P200.

 

Clock

The MHz designation after the CPU is the frequency of the internal timing signal. The motherboard has circuitry that generates an "external" timing signal known as the clock. The CPU internal timing is a multiple of this external one.

Memory

RAM packages

The photograph at left shows a portion of a motherboard with two 72-pin and four 30-pin SIMM slots. Both are phased out. Current motherboards use SDRAM that comes packaged on 168-pin DIMM modules with a typical memory speed of 10ns.

Cache

Cache is short for associative cache memory. This memory is faster, but far more expensive, and hence smaller. There are Level 1, Level 2, and Level 3 caches. L1 is on the same silicon chip as the CPU. L2 is off-chip cache. Motherboards for i486 CPUs typically have 512KB or 1024KB of L2 cache. The Pentium-II and -III CPUs are packaged on a small daughter board with the CPU and 512KB of L2 cache on it. L3 won't be found on PC class machines. When you run out of room on L1, you swap to L2, when you run out of L2, you swap to main memory, when you run out of main memory, you swap to disk.

Bus Types

A bus is a collection of signal lines. On current motherboards for desktop PCs, you will see PCI, AGP, and ISA busses. The bus types known as VLB, EISA, MCA are obsolete. Laptops use PCMCIA (also called PC-card bus). Many PCI cards have a feature called "Plug and Play". These cards negotiate with the operating system at boot time for things like IRQs and DMA channels -- they have no jumpers. Unix fans call this feature "plug-and-pray."

Video controllers

Modern video controllers are independent computer subsystems, with their own processor(s) and RAM, that work in parallel with the CPUs on the motherboard. Video controllers translate byte values deposited in their video memory by Windows or an X11 server under Linux into an analog RGB signal which drives your monitor. The simplest kinds treat their video memory as one big frame buffer, requiring the CPU to do all dot-painting. More sophisticated ``accelerated'' cards offer operations such as BitBlt.

Monitors

Monitors are often CRTs. The vertical frequency is the upper limit of the monitor's flicker rate; 60Hz is minimal for ergonomic comfort, 72Hz is VESA-recommended, and > 80Hz is good. Dot pitch is the physical resolution of the screen's phosphor mask. We expect TFT active matrix screens based on LCD to replace even the desktop CRT displays.

Power Supply

floppy disk power hard disk power    A PC power supply converts the AC power  to 5V and 12 V DC. The 12 V supply need only supply a rather small amount  of current. So, a so-called 130-watt power supply can deliver  approximately 25 A at 5V.

Hard Disks

Currently (1999) the hard disk types that are on the market are: EIDE and SCSI. The performance of a hard disk is dictated by its rotational speed (5400 to 10000 rpm, the higher the better), and seek time (9 to 15 msec, the lower the better). Generally speaking, the SCSI disks are faster and higher in capacity and hence costlier than EIDE.

Disk Partitions

A large disk, say of 10 GB, can be logically divided into 10 "partitions" each of 1 GB by grouping a series of disk cylinders. The info regarding this grouping is written on the hard disk itself as the partition table. In Windows, each partition is referred to by a letter-colon syntax. In Linux, they have the /dev/hda form.

BIOS

BIOS is pre-loaded into flash memory.  AMI, Award, and Phoenix are some of the developers of BIOS.  At boot time, the screen content and user interface are different, but the functionality that all these BIOS present to the operating system is the same.

Linux Operating System

You are all familiar with Microsoft Windows. The Linux Operating System is a Unix clone that volunteers developed in their own free time. Currently, it ranks as Number 2 in the number of installations world-wide if we group all versions of Windows into one.

Play with Linux

Applications are located in the directories named /bin, /usr/bin, /usr/X11R6/bin, and /usr/X11R6/lib/xscreensaver. We loaded the X11 window manager called icewm. Try the various themes it has. Our PC is a lowly 486/33, that is also starved for RAM, so be patient though. In particular, run the "screensaver" programs named maze and bouboule. Can you describe the mathematical models that form their bases?

HP Vectra PCs

For experimentation in EGR 199, we bought several HP Vectra PCs from the WSU surplus store (ESPM). These were made in 1993. They have Please refer to the HP Vectra 5/xxx User's Guide if you need help in locating components or in opening the box.

 

Procedures

Assembling the PC

There are ten hard disks available: five are pre-loaded with Windows 3.1 and the other five are preloaded with Linux 2.2.X. Collect the following from your TA.

 
  1. One open PC box, with motherboard, power supply, and cables, but no SIMMS
  2. Three 72-pin SIMMs, each of 4MB
  3. One CRT monitor
  4. One keyboard
  5. One mouse
  6. One Windows 3.1 loaded hard disk
  7. One Linux-loaded hard disk.
  8. One DOS boot floppy diskette.
  9. One Linux boot floppy diskette.

Precautions

     

  1. Make sure that you aren't full of static electricity--it can zap and ruin components. Touch the metal case of the PC, every once in a while, to discharge static.
  2. Never turn the power off, or press the Reset button without shutting the system down properly. If you do, in all likelihood, the hard disk content is trashed. Several files are cached in RAM that need to be written out to the hard disk before the system shuts down. "Proper shut down" of the system is initiated by pressing the Control-Alt-Delete keys simultaneously.
  3. In the following, whenever we ask you to add or remove a hardware component, make sure that you shut the machine down properly, turn the power switch (on the front panel) off, and also unplug the power chord from the back of the case. You can leave the monitor turned ON through out.
  4. Remember to align the ribbon cable's red-edge with pin 1 on both the floppy and hard disk connectors.

Power On Self Test

  1. Discharge any static electricity built up on you by touching the metal case of the PC box. Make sure the power switch on the front panel is off, and the power cable is disconnected.
  2. Connect the motherboard power cable from the power supply to the plug that is on the vertical backplane. It is polarized, and unless you use extreme force, it is not possible to connect incorrectly. (It is possible that it is already connected from a previous lab.)
  3. Insert one SIMM in its slot.
  4. Connect the CRT monitor video cable to the SVGA connector on the PC box. Turn the power on the CRT.
  5. Leave the floppy disk, hard disk, and keyboard, and mouse unconnected.
  6. Connect the power cable to the power supply, but do NOT turn the power switch on the PC box on yet.
  7. Write the answers to the following questions, with explanations in addition to yes/no, on the Achievement Test:

    Q1: Do you think the PC will boot?
    Will some error occur?

  8. Now, turn the power on the PC box. Watch what is being displayed on the screen. Record what you have seen.
  9. Turn the power off on the front panel, and disconnect the power cable.
  10. Q2: Suppose we did not insert the SIMM. Do you think the PC would have booted? Explain.

Booting from Floppy Disk

  1. Discharge any static electricity built up on you by touching the metal case of the PC box. Make sure the power switch on the front panel is off, and the power cable is disconnected.
  2. Check that everything (except power) is connected as in Power On Self Test above.
  3. Connect the floppy disk ribbon cable to the back plane. Remember to align the ribbon cable's red-edge with pin 1. Connect the other end of the cable to the floppy disk drive. Attach the floppy power connector.
  4. Leave the mouse and hard disk unconnected.
  5. Connect the keyboard.
  6. Connect the power cable, and turn the power on. The floppy drive should be without any disk in it. Wait until the PC completes the boot process. Note in your journal the error message and its context.

    7. Booting from Floppy into DOS

     

  7. Insert the DOS boot disk. Push the reset button on the front panel. Wait until the PC completes the boot process. Invoke the command

    dir/a > dirlst.txt

  8. Terminate this session by pressing Control-Alt-Delete simultaneously.

    9. Booting from Floppy into Linux

  9. Insert one more SIMM in its slot. Booting into Linux from the supplied floppy disk needs a total of at least 8 MB of RAM.
  10. Insert the Linux boot disk. Push the reset button on the front panel. Wait until the PC completes the boot process. No login is required. Invoke the command

    ls -lisa > dirlst.txt

  11. Terminate this session by pressing Control-Alt-Delete simultaneously. Wait for the BIOS screen display to appear, and at that moment ...
  12. Turn the power off on the front panel, and disconnect the power cable.
  13. Remove the floppy disk from the drive.

Booting from Windows 3.1 Hard Disk

     

  1. Check that everything (except power) is connected as in Booting from Floppy Disk above.
  2. Carry out the following steps with just one SIMM first, and then insert the second SIMM in its slot and do the steps again.
  3. Discharge any static electricity built up on you by touching the metal case of the PC box. Make sure the power switch on the front panel is off, and the power cable is disconnected.
  4. Connect the hard disk ribbon cable to the back plane. Connect the other end of the cable to the Win3.1 hard disk. Attach the power connector to the hard disk.
  5. Make sure that there is no floppy disk in the drive.
  6. Make sure that the power cable is connected. Turn the power on. Wait until the PC completes the boot process.
  7. Play with Win 3.1: Just try as many commands, games and applications as you can, say for about 10 minutes.
  8. Terminate this session by pressing Control-Alt-Delete simultaneously. Wait for the BIOS screen display to appear, and at that moment ...
  9. Turn the power off on the front panel, and disconnect the power cable.
  10. Disconnect the ribbon cable and power cable from the Windows 3.1 disk. Set this hard disk aside.

Booting from Linux Hard Disk

  1. Discharge any static electricity built up on you by touching the metal case of the PC box. Make sure the power switch on the front panel is off, and the power cable is disconnected.
  2. Check that everything (except power) is connected as in Booting from Floppy Disk above.
  3. Connect the hard disk ribbon cable to the back plane. Connect the other end of the cable to the Linux hard disk. Attach the power connector to the hard disk.
  4. Make sure that there are three SIMMs in their slots.
  5. Make sure there is no floppy disk in the drive.
  6. Connect the power cable, and turn the power on. Wait until the PC completes the boot process, and the Login screen appears. Login as guest, with password as guest00 (guest-zero-zero).
  7. Play with Linux: Applications are located in the directories named /bin, /usr/bin, /usr/X11R6/bin, and /usr/X11R6/lib/xscreensaver. We loaded the X11 window manager called icewm. Try the various themes it has. Our PC is a lowly 486/33, that is also starved for RAM, so be patient though. In particular, run the "screensaver" programs named maze and bouboule. Can you describe the mathematical models that form their bases?
  8. Logout
  9. Terminate this session: Press Control-Alt-F1 simultaneously. This will switch from the X11 screen to text screen. Now, press Control-Alt-Delete simultaneously. Wait for the BIOS screen display to appear, and at that moment ...
  10. Turn the power off on the front panel, and disconnect the power cable.
  11. Disconnect the ribbon cable and power cable from the Linux hard disk. Set this hard disk aside.

 

Concluding Activities

Assemble the PC to the way it was when you began this lab. Return all components to your TA. Follow the instructions given by the TA.

Appendix A: Acronyms

. .
AGP Accelerated Graphics Port
BIOS Basic Input Output System
CPU Central Processing Unit
DIMM Dual In-Line Memory Module. Current.
EIDE Enhanced IDE
IDE Integrated Device Electronics
ISA Industry Standard Architecture
LAN Local Area Network
MIPS Million Instructions Per Second (unit of CPU perf)
MFLOPS Million Floating-point Operations Per Sec (unit of CPU perf)
PCI Peripheral Component Interconnect
ROM Read Only Memory
SCSI Small Computer System Interface
SDRAM Synchronous Dynamic RAM
SIMM Single In-Line Memory Module, 30- or 72-pin. Obsolete
A few acronyms and their expansions are collected in the table here. Or, if you wish, type the acronym or term in the input box below, and then press return or the define button to look it up in the TechEncyclopedia.

Appendix B: Further Reading Links

pclt.cis.yale.edu/pclt/ PC Lube and Tune up
web.sunyocc.edu/~lewism/pc.html PC Building and Troubleshooting
www.sharkyextreme.com/hardware/memory_guide/ Guide to RAM, SDRAM, ...
www.tomshardware.com Hardware Review site with Guides
http://www.annoyances.org/ Are you annoyed at Windows?
http://slashdot.org/ A Linux advocacy site
http://themes.org/ Showcase X11 Desktop Themes

Appendix C: Dave Barry on Computers

Hardware: This is the part of the computer that stops working when you spill beer on it.

Software: These programs give instruction to the CPU, which processes billions of tiny facts called bytes, and within a fraction of a second it sends you an error message that requires you to call the customer-support hot line and be placed on hold for approximately the life-span of a caribou.

Megahertz: This is really, really big hertz.

RAM: This gives guys a way of deciding whose computer has the biggest, studliest memory. That's important, because the more memory a computer has, the faster it can produce error messages.

Internet is the single most important development in the history of human communications since the invention of call-waiting. A bold statement? Indeed, but consider how the internet can enhance our lives. Imagine that you need to: 1. make an airline reservation; 2. buy concert tickets; 3. research a tax question; and 4. help your child with a school report. Now you simply turn on your computer, dial up your Internet access number, and in less than an instant you're listening to a busy signal!

 

Dave Barry, "Get With The Program,"
Reader's Digest, July 1997

Achievement Test

The achievement test is replaced with a journal, in which you record the answers to various questions posed as you proceed in the experiments. Pointers to all these questions are collected below; click on them to see the context for the questions. You are working in groups of two but these answers must be your own.
  1. What do you think the causes are for the short sighted remarks made by Olson and Watson?
  2. Summarize your visits to the Web sites mentioned in Suggested Preparation.
  3. Answer Q1, Q2 of Power on Self Test.
  4. Summarize what you did for [Play with Win 3.1].
  5. Summarize what you did for [Play with Linux] .
Send comments to pmateti@cs.wright.edu
09/20/99 06:49:51 PM