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Jai Ganesh

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Motherboard

Motherboard

Details

A motherboard (also called mainboard, main circuit board, MB, mboard, backplane board, base board, system board, mobo; or in Apple computers logic board) is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.

Motherboard means specifically a PCB with expansion capabilities. As the name suggests, this board is often referred to as the "mother" of all components attached to it, which often include peripherals, interface cards, and daughterboards: sound cards, video cards, network cards, host bus adapters, TV tuner cards, IEEE 1394 cards, and a variety of other custom components.

Similarly, the term mainboard describes a device with a single board and no additional expansions or capability, such as controlling boards in laser printers, television sets, washing machines, mobile phones, and other embedded systems with limited expansion abilities.

History

Mainboard of a NeXTcube computer (1990) with microprocessor Motorola 68040 operated at 25 MHz and a digital signal processor Motorola 56001 at 25 MHz, which was directly accessible via a connector on the back of the casing.
Prior to the invention of the microprocessor, the digital computer consisted of multiple printed circuit boards in a card-cage case with components connected by a backplane, a set of interconnected sockets. In very old designs, copper wires were the discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The central processing unit (CPU), memory, and peripherals were housed on individually printed circuit boards, which were plugged into the backplane. The ubiquitous S-100 bus of the 1970s is an example of this type of backplane system.

The most popular computers of the 1980s 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.

During the late 1980s and early 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard. In the late 1980s, personal computer motherboards began to include single ICs (also called Super I/O chips) capable of supporting a set of low-speed peripherals: PS/2 keyboard and mouse, floppy disk drive, serial ports, and parallel ports. By the late 1990s, many personal computer motherboards included consumer-grade embedded 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. Business PCs, workstations, and servers were more likely to need expansion cards, either for more robust functions, or for higher speeds; those systems often had fewer embedded components.

Laptop and notebook computers that were developed in the 1990s integrated the most common peripherals. This even included motherboards with no upgradeable components, a trend that would continue as smaller systems were introduced after the turn of the century (like the tablet computer and the netbook). Memory, processors, network controllers, power source, and storage would be integrated into some systems.

Design

The Octek Jaguar V motherboard from 1993. This board has few onboard peripherals, as evidenced by the 6 slots provided for ISA cards and the lack of other built-in external interface connectors. Note the large AT keyboard connector at the back right is its only peripheral interface.

The motherboard of a Samsung Galaxy SII; almost all functions of the device are integrated into a very small board
A motherboard provides the electrical connections by which the other components of the system communicate. Unlike a backplane, it also contains 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 microcomputers, 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:

* CPU sockets (or CPU slots) in which one or more microprocessors may be installed. In the case of CPUs in ball grid array packages, such as the VIA Nano and the Goldmont Plus, the CPU is directly soldered to the motherboard.
* Memory slots into which the system's main memory is to be installed, typically in the form of DIMM modules containing DRAM chips can be DDR3, DDR4, DDR5, or onboard LPDDRx.
* The chipset which forms an interface between the CPU, main memory, and peripheral buses
* Non-volatile memory chips (usually flash memory in modern motherboards) containing the system's firmware or BIOS
* The clock generator which produces the system clock signal to synchronize the various components
* Slots for expansion cards (the 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
* Connectors for hard disk drives, optical disc drives, or solid-state drives, typically SATA and NVMe now.

Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as USB for mouse devices and keyboards. 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.

Form factor

Motherboards are produced in a variety of sizes and shapes called form factors, some of which are specific to individual computer manufacturers. However, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2005, most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, which have not been built from commodity components. A case's motherboard and power supply unit (PSU) form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases. For example, an ATX case will usually accommodate a microATX motherboard. Laptop computers generally use highly integrated, miniaturized, and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair. Often the failure of one laptop component requires the replacement of the entire motherboard, which is usually more expensive than a desktop motherboard.

CPU sockets

A CPU socket (central processing unit) or slot is an electrical component that attaches to a printed circuit board (PCB) and is designed to house a CPU (also called a microprocessor). It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB. CPU sockets on the motherboard can most often be found in most desktop and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture. A CPU socket type and motherboard chipset must support the CPU series and speed.

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.

Peripheral card slots

A typical motherboard will have a different number of connections depending on its standard and form factor.

A standard, modern ATX motherboard will typically have two or three PCI-Express x16 connection for a graphics card, one or two legacy PCI slots for various expansion cards, and one or two PCI-E x1 (which has superseded PCI). A standard EATX motherboard will have two to four PCI-E x16 connection for graphics cards, and a varying number of PCI and PCI-E x1 slots. It can sometimes also have a PCI-E x4 slot (will vary between brands and models).

Some motherboards have two or more PCI-E x16 slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for AMD). These allow 2 to 4 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming, video editing, etc.

In newer motherboards, the M.2 slots are for SSD and/or wireless network interface controller.

Temperature and reliability

Motherboards are generally air cooled with heat sinks often mounted on larger chips in modern motherboards. Insufficient or improper cooling can cause damage to the internal components of the computer, or cause it to crash. Passive cooling, or a single fan mounted on the power supply, was sufficient for many desktop computer CPU's until the late 1990s; since then, most have required CPU fans mounted on heat sinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additional computer fans and integrated temperature sensors to detect motherboard and CPU temperatures and controllable fan connectors which the BIOS or operating system can use to regulate fan speed. Alternatively computers can use a water cooling system instead of many fans.

Some small form factor computers and home theater PCs designed for quiet and energy-efficient operation boast fan-less designs. This typically requires the use of a low-power CPU, as well as a careful layout of the motherboard and other components to allow for heat sink placement.

A 2003 study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions to I/O read/write errors, can be attributed not to software or peripheral hardware but to aging capacitors on PC motherboards. Ultimately this was shown to be the result of a faulty electrolyte formulation, an issue termed capacitor plague.

Modern motherboards use electrolytic capacitors to filter the DC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water based electrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due to voltage instabilities. While most capacitors are rated for 2000 hours of operation at 105 °C (221 °F),[8] their expected design life roughly doubles for every 10 °C (18 °F) below this. At 65 °C (149 °F) a lifetime of 3 to 4 years can be expected. However, many manufacturers deliver substandard capacitors,[ which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures around the CPU socket exacerbate this problem. With top blowers, the motherboard components can be kept under 95 °C (203 °F), effectively doubling the motherboard lifetime.

Mid-range and high-end motherboards, on the other hand, use solid capacitors exclusively. For every 10 °C less, their average lifespan is multiplied approximately by three, resulting in a 6-times higher lifetime expectancy at 65 °C (149 °F). These capacitors may be rated for 5000, 10000 or 12000 hours of operation at 105 °C (221 °F), extending the projected lifetime in comparison with standard solid capacitors.

In Desktop PCs and notebook computers, the motherboard cooling and monitoring solutions are usually based on Super I/O or Embedded Controller.

Additional Information

A motherboard is the main printed circuit board (PCB) in a computer. The motherboard is a computer's central communications backbone connectivity point, through which all components and external peripherals connect.

Motherboards can be found in virtually all computers, especially desktop and laptop PCs. The components that connect through them include chipsets, central processing units (CPU) and memory. The external peripherals include Wi-Fi, Ethernet and graphics cards with the graphics processing unit, or GPU.

Motherboard manufacturers include Acer, ASRock, Asus, Gigabyte Technology, Intel and Micro-Star International.

How do motherboards work?

The PCB of a large motherboard may include six to 14 layers of fiberglass, copper connecting traces and copper planes for power and signal isolation. Other components get added to a motherboard through expansion slots. These include processor sockets; dual in-line memory modules; Peripheral Component Interconnect (PCI), PCI Express (PCIe) and solid-state drive M.2 slots; as well as power supply connections.

A heatsink and fan manage the heat components such as the CPU generate. Typically motherboards offer additional connectivity through a Southbridge chip such as PCI, Serial Advanced Technology Attachment or SATA, Thunderbolt, USB and other interfaces.

The CPU is generally connected to double data rate 3 (DDR3), DDR4, DDR5 or onboard LPDDRx RAM and PCIe. This is done through point-to-point interconnects such as HyperTransport, Intel's QuickPath Interconnect and Ultra Path Interconnect. Choosing a motherboard often determines many features a computer will support.

Motherboard designs in desktop computers typically are the ATX motherboard, which is Intel's improved version of IBM's AT design. Other form factor designers include the following:

* extended ATX
* mini-ATX
* micro ATX
* BTX
* micro BTX
* mini-ITX
* micro ITX
* nano-ITX

Some memory controllers are now built into CPUs; that has eliminated the Northbridge chips that provided memory management from the motherboard. Integrated video has moved from a motherboard slotted peripheral to graphics-enabled CPUs.

AMD's Ryzen has a system-on-a-chip design that also makes the Southbridge chipset optional. This CPU integration has cut motherboard manufacturers' costs. They can offer base systems for workstations and entry-level computers and can design customized implementations for various processors that enable platform upgrades.

Gaming motherboards are made for high-performance computers; they are more powerful and have more features than motherboards for desktop and laptop computers.

A typical motherboard contains the CPU, memory, storage, ROM BIOS, Southbridge and Northbridge chipsets, cooling fans, peripheral connector slots, connectors for peripheral devices, the battery backup and the power connector.

Motherboard components

Each motherboard is designed to support specific components, such as CPUs and memory. They can accommodate most types of hard drives and peripherals.

Motherboards include the following primary components:

* CPU with its logic circuitry that processes the instructions from programs, the operating system and other computer components;
* memory where instructions and data are temporarily stored and executed;
* storage interface for solid-state or hard disk drive for persistent data and application storage;
* ROM BIOS providing non-volatile memory that stores firmware, such as the basic input/output system or BIOS;
* Northbridge chipset that connects CPU, memory, storage and other components;
* Southbridge chipset that connects peripheral elements to the motherboard and connects to the Northbridge;
* cooling fans that maintain a suitable internal operating temperature;
* peripheral connector slots for plugin peripheral cards, such as graphics and communications adapters;
* connectors for peripheral devices such as USB ports and other connectors for external devices;
* the backup battery that ensures key system configuration data is maintained when main power is unavailable; and
the power connector, connecting to an external power source.

Many other elements comprise a typical motherboard. Think of a motherboard as a large mosaic of electrical connections linking the various parts of a computer.

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