Mainboard : History

Prior to the advent of the Apple II in 1977, a computer was usually built in a case or mainframe with components connected by a backplane consisting of set of slots themselves connected with wires. The CPU, memory and I/O peripherals were housed on individual PCBs or cards which plugged into the backplane.

With the arrival of the microprocessor, it became more cost-effective to place the backplane connectors, processor and glue logic onto a single "mother" board, with video, memory and I/O functions on "child" cards — hence the terms "motherboard" and daughterboard. The Apple II computer featured a motherboard with 8 expansion slots.

The early pioneers of motherboard manufacturing were Micronics, Mylex, AMI, Hauppauge, Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based manufacturers.

During the late 1980 and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard (see above). In the late 1980s, motherboards began to include single ICs (called Super I/O chips) capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel ports. As of the early 2000s, many motherboards support a full range of audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retain only the graphics card as a separate component.

Integrated peripherals

With the steadily declining costs and size of integrated circuits, it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB, the physical size and total cost of the system may be reduced; highly-integrated motherboards are thus especially popular in small form factor and budget computers.

For example, the ECS RS485M-M, a typical modern budget motherboard for computers based on AMD processors, has on-board support for a very large range of peripherals:

1.disk controllers for a floppy disk drive, up to 2 IDE/PATA drives, and up to 4 SATA drives (including RAID 0/1 support)

2.integrated ATI Radeon graphics controller supporting 2D and 3D graphics, with VGA and TV output

3.integrated sound card supporting 6-channel audio and SPDIF output

4.fast Ethernet network controller for 10/100 Mbps networking

5.USB 2.0 controller supporting up to 8 USB ports

6.IrDA controller for infrared communications (e.g. with a handheld remote control)

7.temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components

Expansion cards to support all of these functions would have cost hundreds of dollars even a decade ago, however as of April 2007 such highly-integrated motherboards are available for as little as $30 in the USA.

Mainboard : Components and functions

The motherboard of a typical desktop consists of a large PCB. It holds electronic components and interconnects, as well as physical connectors (sockets, slots, and headers) into which other computer components may be inserted or attached.

Most motherboards include, at a minimum:

1. sockets in which one or more CPUs are installed

2. slots into which the system's main memory is installed (typically in the form of DIMM modules containing DRAM chips)

3. a chipset which forms an interface between the CPU's front-side bus, main memory, and peripheral buses

4. non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS

5. a clock generator which produces the system clock signal to synchronize the various components

6. slots for expansion cards (these interface to the system via the buses supported by the chipset)

7. power connectors which receive electrical power from the computer power supply and distribute it to other components

Additionally, nearly all motherboards include logic and connectors to support commonly-used input devices, such as PS/2 connectors for a mouse and keyboard. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.

Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heatsinks and mounting points for fans to dissipate excess heat.