1. The Visible PC
Chapter 1

2. Central Processing Unit (CPU)
also called “microprocessor”
performs all the calculations that take place inside a PC
have a cooling fan
have a make and model
Intel Pentium / AMD Athlon, etc.

3. CPU’s (continued)
measure potential performance with a clock speed measured in megahertz
first CPU MHz
today CPU MHz = 1GHz
come in different packages
Pin Grid Array (PGA) * most common
Single Edge Cartridge (SEC)

4. Random Access Memory (RAM)
stores programs and data currently being used by the CPU
measured in units called bytes or megabytes
average PC will have from MB
DIMM’s and SIMM’s
Dual Inline Memory Module
most common today pin
Single Inline Memory Module
basically obsolete

5. RAM (continued) 2 most common sizes of SIMM’s
30 pin and 72 pin
3 most common sizes of DIMM’s
168 pin
2 Small Outline DIMM’s 72 and 144 pin (used for laptops mostly)

6. Motherboard “chassis of an automobile”
everything connects directly or indirectly to it
thin, flat piece of circuit board
contains sockets and connectors for various components of the PC
use tiny wires called “traces” to connect the various components

7. Motherboard (continued)
use multipurpose expansion slots to add optional components
expansion cards plug into the expansion slots

8. Power Supply provides the necessary electrical power
takes 110-volt AC power and converts it into 12-volt, 5-volt, and 3.3-volt DC power

9. Floppy Drives two types of floppy drives
3.5 inch (common) / 5.25 inch (old)
connects via a 34-pin ribbon cable
floppy cables are unique in 2 ways
narrowest ribbon cable (approx. 1.5 in. wide)
has a twist in the middle
they need power so they have a connector which attaches to the power supply

10. Hard Drive store programs and data that are not currently being used
capacity measured in megabytes like RAM
cap. can vary from 500 MB - 75 GB
average PC will have 1 HD but can accept up to 4

11. Hard Drives (continued)
2 common types of HD’s
EIDE and SCSI
95% of PC’s use EIDE although both can coexist in one
EIDE - 40 pin, 2 in. cable
SCSI - 50 pin, 2.5 in. cable
SCSI can connect many different devices and will be discussed in detail later

12. CD-ROM Drive used to have their own special controllers
now they run on EIDE or SCSI controllers
most PC’s have an EIDE hard drive and a EIDE CD-ROM Drive on one controller

13. Connectors
although PC’s use 50 different connectors, almost all connectors fit into one of seven major types:
DB - BNC
DIN - audio
Centronics - USB RJ

14. Connectors DB Connectors DIN Connectors have a slight “D” shape
can have from 9 to 37 pins, but rarely more than 25
can be male/female
DIN Connectors
2 sizes: DIN and mini-DIN
always female

15. Connectors Centronics RJ Connectors
also “D” shaped, but have a large central tab and contacts instead of pins
have wings to lock in place
rarely see in back of PC, but almost every printer in existence has 36-pin socket
RJ Connectors
RJ-11 - used for modems
RJ-45 - used for network cabling

16. Connectors BNC Connectors Audio Connectors
commonly referred to as coax connector
slowly fading, most PC’s use RJ-45 now
similar to the connection on back of your TV
Audio Connectors
used exclusively on sound cards and are exactly like the plug for headphones on a walkman

17. Connectors Universal Serial Bus (USB) Connectors FireWire Connectors
distinctive rectangular shape
devices are hot-swappable
allows you to daisy-chain up to 127 devices
FireWire Connectors
also known as IEEE 1394
moves data at incredibly high speeds making popular for streaming video

18. Sound Cards perform 2 functions
take digital information and turn it into sound
take sound that is input and turn it into digital
all sound cards have jacks for speakers and a microphone, and a line-in and line-out
most provide a 15 pin DB socket that enables you to attach an instrument or joystick
also can connect to CD-ROM

19. Video and Network Cards
Video Cards
15-pin female DB connector, 3 rows of pins
nothing else like it on the back of PC
Network Cards
will have one or more of the following types of connectors: RJ-45, BNC, 15-pin 2 row female DB, or 9-pin fem. DB

20. Keyboard / Mouse / Modem
2 main types AT DIN and PS/2 style mini DIN
Mouse
2 sizes: 25-pin (older) / 9-pin (most common)
many PC’s use USB for the mouse so there’s not excessive cable lying around in the PC
Modem
external and internal
have 2 RJ-11 sockets

21. Printer / Joystick Printer Joystick
Use a parallel port as opposed to serial
use a 25-pin female DB connector
Joystick
use a 15-pin female DB connector
originally used as a mouse, now just used for games

22. Jumpers and Switches
Jumpers - tiny pins, usually half a centimeter long
shunts connect pins to create a circuit
jumpers without a shunt - open or off
jumpers with a shunt - closed or on
if a shunt is on only one pin and not connecting it is considered parked

23. Jumpers and Switches Switches
same thing as jumpers but you don’t have to worry about losing the shunts
use a small screwdriver or a mechanical pen to flip the switches, not a pencil or pen
there is no industry standard for jumpers and switches so you must read the documentation on the particular PC to know which one is which