Identifying Parts
AGP
USB
Form Factor
Voltage
BIOS
Chipsets
Cache

Desktop memory

General Information
PC100 Specification
Future memory

Processors

General Information
Future Intel processors
Future AMD processors
Socket 7 versus Slot One

Storage

Floppy Drives
IDE Hard Drives
CD-ROM Drives

Motherboard Diagram

Click on the image to enlarge

Peripheral Controller
This piece of silicon controls the I/O ports (input/output) on the mainboard. The features incorporated in these controllers varies based on the application and the manufacturer:  IDE control logic, serial ports, IEEE 1284 parallel port (Enhanced Parallel Port (EPP) and Extended Capabilities Port (ECP)), floppy disk controller, Real Time Clock (RTC), and keyboard controller (KBC). 

There are several manufacturers which supply motherboard companies with I/O controllers.  ALi, Winbond, and National Semiconductor are just three common companies.

• The Super I/O Controllers from National Semiconductor are PC87306, PC87307, PC87323VF.
• The Winbond W83977TF is made to fully comply with Microsoft PC97 Hardware Design
  Guide. IRQs, DMAs, and I/O space resource are flexible to adjust to meet ISA PnP
  requirement.
• ITE produces the IT8661F as well as the first 100 pin packaged peripheral controller.
• Acer Laboratories Inc (ALi) also manufacturers a serial/parallel controller meeting the Pentium II specifications: supporting PC98, Win98, NT 5.0, and FIR (Fast Infra Red).

Keyboard Connector

An AT or PS/2 keyboard plugs into the keyboard connector located at the back of the motherboard.  An AT form factor motherboard uses the larger din plug with 5 pins.  There are PS/2 compatible keyboards on the market which use a mini-din with 6 pins.  Most ATX form factor boards use the mini din connector.

Parallel and Serial connectors

• AT

A small ribbon cable attaches to these headers. The parallel devices and serial devices attach to these ribbon cables; such as a parallel printer or serial mouse.  There are two types of cables, Everex or IBM pinout.

• ATX

The parallel and serial ports are built onto the back of the motherboard.

Power Connector (AT or ATX)

• AT

Two power leads from the power supply plug into this connector.  During a cocktail party, the “in crowd” will commonly discuss the correct orientation of these wires.  Fortunately, the truly up to date members have already changed to an ATX power supply which requires only a single connector.

• ATX

A single connector with a double row of wires.

Floppy and IDE Connectors
Permanent storage devices attach to these headers. The cables for the floppy drive and IDE drives plug into these headers.  Many times the manufacturer has taken pity on us and silk screened the “Pin one” designation so that we know how to correctly orient the ribbon cables.  If the drive light is always on your floppy drive - Oops.  You need better glasses.

Memory

• SIMM Sockets

72-pin memory modules fit into sockets on the mainboard.

• DIMM Sockets

168-pin memory modules fit into these sockets.  The socket is designed so that the modules will only fit in one direction.  The modules are also “keyed” with notches so that buffered modules do not fit in unbuffered sockets.

Oscillator Clock
A circuit that generates a series of pulses that pace the electronic system within the computer, thus pacing, synchronizing, and coordinating the operations of the computer’s circuit.

Intel PCIset
The chipset designed by Intel.  The 430VX, 430HX, 430TX, 440FX, and 440LX, 440BX.  Many Super 7 boards use SiS, VIA, and ALI.

L2 Cache
The secondary cache known as Level-2 acts as a buffer between the CPU and core memory.  The processors designed by Intel, AMD, and Cyrix have a smaller L1 cache built into their CPU.  The Intel Pentium Pro and Pentium II have the L2 cache built within the packaging and none is required on the mainboard.

Processor attachment

• ZIF Socket 7

The Zero Insertion Force socket in which the processor sits.  The lever helps the user remove the CPU or lock the CPU into place and keep a tight electrical connection.

• Slot One

Pentium II family of processors attaches to the mainboard through a slot.

• Slot Two

LED connections
The power Light Emitting Diodes,  the hard drive LEDs, Keyboard lock, and other indicators on the enclosure connect to these headers.

Switching Voltage Regulator
This coil regulates the power supplied by the power supply.  The power supply provides 3.3v, 5v, and 12v.

CMOS battery
Complimentary Metal Oxide Semiconductor.  When the power of the mainboard is not present, this battery is low powered enough to help the silicon keep the required information as to the configuration of the PC.

Basic Input Output System (BIOS)
This ROM chip controls the low level interactions between hardware and software.

Expansion slots

• PCI Slots

These expansion slots follow the Peripheral Component Interconnect specifications as proposed by the PCI SIG (Special Interest Group).   You can view a PDF file comparing PCI revision 2.0 and 2.1 on the Intel website.

• ISA Slots

These expansion slots follow the Industry Standard Architecture as found on the early PCs introduced by the IBM AT.

Nylon Standoffs
The motherboard is attached to the enclosure by Nylon standoffs and grounding screws.  One metal screw will allow the motherboard and enclosure to be of equal charge.  Some mainboards need to be “free” from the enclosure while others require grounding.