Motherboard Introduction
The motherboard is the main printed circuit board (PCB) of the PC and its components. In today's PC systems the most common design for motherboards is the ATX design, a follow up of the AT board, based on the IBM AT motherboard. Most of the basic components that come with a system board are:
- CPU (including L1 and L2 cache static RAM memory),
- two other large chips (the 'chipset': Northbridge and Southbridge),
- external memory (dynamic RAM, optional L3 static RAM cache),
- peripheral buses (5 or 6 PCI, 1 AGP; optional: ISA, 'riser cards')
- ports/connectors and Super I/O chip(serial, parallel, game port, PS/2 mouse/keyboard, infrared interface, floppy disk controller, fan RPM control, etc. all linked to the Super I/O chip; USB, SMBus, connectors for HDD, DVD, CD-drives, etc.),and
- some smaller components such as the voltage regulator module (VRM), a small battery (to safeguard clock settings and motherboard configuration), jumpers (unless integrated in the BIOS), a (reprogrammable) FLASH memory that holds the software for the BIOS (Basic Input Output System.
Intel calls their BIOS chip Firmware Hub (FWH)) and a CMOS chip that holds the motherboard configuration (sits in the NVRAM portion of the chip) and the Real Time Clock (RTC).
Additionally, desktop PC vendors may have on-board audio and telephony (modem/networking) facilities, typically connected to the AC (Audio Codec) Link signals of the Southbridge.
For mobile PC motherboards the peripheral slots are limited to typically 2 PCMCIA slots and the rest is on the motherboard. Graphics chips (typically external through AGP in a desktop) are embedded in the motherboard, as are audio, network cards, modems, etc..
Courtesy of the French Energy Agency ADEME, Future Electronics project.
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