Motherboard - Design

Design

A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also connects the central processing unit and hosts other subsystems and devices.

A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables, in modern computers it is increasingly common to integrate some of these peripherals into the motherboard itself.

An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.

Modern motherboards include, at a minimum:

• sockets (or slots) in which one or more microprocessors may be installed. In the case of CPUs in BGA packages, such as the VIA C3, the CPU is directly soldered to the motherboard.
• Slots into which the system's main memory is to be installed (typically in the form of DIMM modules containing DRAM chips)
• A chipset which forms an interface between the CPU's front-side bus, main memory, and peripheral buses
• Non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS
• A clock generator which produces the system clock signal to synchronize the various components
• Slots for expansion cards (these interface to the system via the buses supported by the chipset)
• Power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards. As of 2007, some graphics cards (e.g. GeForce 8 and Radeon R600) require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply. Most disk drives also connect to the power supply via dedicated connectors.

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. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. 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 heat sinks and mounting points for fans to dissipate excess heat.