Computing – Form and function of a motherboard


The motherboard (mainboard) is the main circuit board of a computer. On it, the individual components such as the main processor are (CPU), memory, the BIOS chip with embedded firmware, the interface modules and slots for expansion cards, the necessary circuit paths are divided into several layers.


The motherboard contains slots for the processor, memory modules and expansion cards such as graphics, sound and network cards as well as modules that connect the components together.

The previous division into a Northbridge for high-performance connection of memory and graphics card and a Southbridge for hard drive, PCI slots and peripherals is no longer applicable.

Functions such as memory controllers are now integrated into the CPU itself, so a two-chip design was unnecessary. Some still continue to speak of a Southbridge chipset, although it is actually only a key component on the motherboard.

Many former individual components are already permanently integrated on the mainboard (onboard), especially sound and network cards are virtually without exception, they satisfy the needs of many users.

After the acquisition of ATI Technologies, AMD hasĀ  both competitive processors and graphics chips on offer and wants to bring back the single chip design in the upcoming Fusion platform. Already, a graphics core is available in many Intel Core i processors, AMD’s Llano APUs.

While in the past, standard connections such as serial (RS-232) and parallel (LPT) interface have been implemented only on cards, today all the usual ports are already present on the motherboard.

Multiple USB ports are an integral part of each I / O Shields, as well PS/2-ports for mouse and keyboard (some only as a combo port), the aforementioned audio and network connections, and, depending on the orientation of the board, video – , eSATA , FireWire and other ports.

Sometimes, rarely used connections must be swapped for reasons of space to slot panels, so even a game port can be provided. The former variety of different connections for external components is now completely gone and replaced by USB.

Various internal components suh as Serial ATA ports (SATA) are also provided on the motherboard, which has become a standard for hard drives and optical drives.

Apart from graphics cards, hard disk controllers are common components that can provide RAID functionality for up to 28 SAS or SATA hard drives in professional systems.

There are also single or multi-port NICs for copper and fiber optic networks as well as sound cards with extensive digital and analog inputs and outputs. For controller cards, antiquated ports such as RS- 232 PCI interface are quite sufficient, while current USB 3.0 expansion cards are dependent on the high data rate of PCI Express x1 or higher.


The format of the motherboards is distinguished by the form factor. For over ten years, the ATX form factor was common. It solved the time from the AT format, which necessitated several changes to chassis, power supplies and components.

There are several variations of ATX and AT in order to equip more compact devices without proprietary formats, such as Baby AT or uATX. These are listed in the article form factor.

The ATX form factor was to be replaced from 2003 by the incompatible BTX , BTX but could not prevail, and was again taken off the market in 2007.

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