The Visible PCChapter 1

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.

CPU’s (continued) measure potential performance

with a clock speed measured in megahertz first CPU - 4.77 MHz today CPU - 1000 MHz = 1GHz

come in different packages Pin Grid Array (PGA) * most common Single Edge Cartridge (SEC)

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 32 - 128

MB DIMM’s and SIMM’s

Dual Inline Memory Module most common today - 168 pin

Single Inline Memory Module basically obsolete

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)

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

Motherboard (continued) use multipurpose expansion slots

to add optional components expansion cards plug into the

expansion slots

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

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

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

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

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

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

Connectors DB 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

Connectors Centronics

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

Connectors BNC 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

Connectors Universal Serial Bus (USB) 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

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

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

Keyboard / Mouse / Modem Keyboard

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

Printer / Joystick Printer

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

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

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