Motherboard
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[edit] History
Prior to the advent of the microprocessor, a computer was usually built in a card-cage case or mainframe with components connected by a backplane consisting of a set of slots themselves connected with wires; in very old designs the wires were discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The Central Processing Unit, memory and peripherals were housed on individual printed circuit boards which plugged into the backplate. During the late 1980s and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard (see below). 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 late 1990s, many personal computer motherboards supported 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 retained only the graphics card as a separate component.The early pioneers of motherboard manufacturing were Micronics, Mylex, AMI, DTK, Hauppauge, Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based manufacturers.
The most popular computers such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid reverse-engineering and third-party replacement motherboards. Usually intended for building new computers compatible with the exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment
The term mainboard is applied to devices with a single board and no additional expansions or capability. In modern terms this would include embedded systems and controlling boards in televisions, washing machines, etc. A motherboard specifically refers to a printed circuit board with expansion capability.
[edit] Overview
A motherboard, like a backplane, provides the electrical connections by which the other components of the system communicate, but 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, although 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[2]
- 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.[3]
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.
[edit] CPU sockets
[edit] 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,[5] a typical modern budget motherboard for computers based on AMD processors, has on-board support for a very large range of peripherals:
- disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 6 SATA drives (including RAID 0/1 support)
- integrated graphics controller supporting 2D and 3D graphics, with VGA and TV output
- integrated sound card supporting 8-channel (7.1) audio and S/PDIF output
- Fast Ethernet network controller for 10/100 Mbit networking
- USB 2.0 controller supporting up to 12 USB ports
- IrDA controller for infrared data communication (e.g. with an IrDA-enabled cellular phone or printer)
- temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components
[edit] Peripheral card slots
A typical motherboard of 2009 will have a different number of connections depending on its standard.A standard ATX motherboard will typically have one PCI-E 16x connection for a graphics card, two conventional PCI slots for various expansion cards, and one PCI-E 1x (which will eventually supersede PCI). A standard EATX motherboard will have one PCI-E 16x connection for a graphics card, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot. (This varies between brands and models.)
Some motherboards have two PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for ATI). These allow 2 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming and video editing.
As of 2007, virtually all motherboards come with at least four USB ports on the rear, with at least 2 connections on the board internally for wiring additional front ports that may be built into the computer's case. Ethernet is also included. This is a standard networking cable for connecting the computer to a network or a modem. A sound chip is always included on the motherboard, to allow sound output without the need for any extra components. This allows computers to be far more multimedia-based than before. Some motherboards contain video outputs on the back panel for integrated graphics solutions (either embedded in the motherboard, or combined with the microprocessor, such as the Intel HD Graphics). A separate card may still be used [ Read More... ]