The Visible PC Chapter 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 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

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

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

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

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 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 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

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