Temperature and reliability

Motherboards are generally air cooled with heat sinks often mounted on larger chips, such as the northbridge, in modern motherboards. Passive cooling was sufficient for many desktop computer CPUs until the late s; since then, most have required CPU fans mounted on their heatsinks, due to rising clock speeds and power consumption. Most motherboards have connectors for additional case fans as well. Newer motherboards have 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.

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 careful layout of the motherboard and other components to allow for heat sink placement . A study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions to I/O read/write errors, can surprisingly be attributed not to software or peripheral hardware but to aging capacitors on PC motherboards.

Motherboards use electrolytic capacitors for voltage regulation. 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 hours of operation at �C, their expected design life roughly doubles for every �C below this. At �C a lifetime of years can be expected. This appears reasonable for a computer motherboard, however many manufacturers have delivered substandard capacitors, which significantly reduce this life expectancy. Inadequate case cooling and elevated temperatures easily exacerbate this problem. It is possible, but tedious and time-consuming, to find and replace broken capacitors on PC motherboards; it is often cheaper to buy a new motherboard than to pay for such a repair.

History

Prior to the advent of the Apple II in , a computer was usually built in a case or mainframe with components connected by a backplane consisting of a 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 expansion slots.

During the late s and s, it became economical to move an increasing number of peripheral functions onto the motherboard see above. In the late s, 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 s, 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 D gaming and computer graphics typically retain 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.

It can be argued that the motherboard industry was born by IBM in with the release their entry level Personal Computer IBM PC which was based on a motherboard. The motherboard provided an Intel .MHz with K bytes of on-board memory, expandable to K through the use of plug-in memory boards, eight -bit ISA expansion connectors, cassette tape port and keyboard port. All other I/O such as the interface for K -/" floppy drives, serial and parallel ports were provided by plug-in boards. IBM approached Digital Research about using DR/DOS as an operating system but was rebuffed. IBM approached Microsoft and licensed PC-DOS. Microsoft released PC-DOS . in by retaining rights to the operating system allowing them to sell it to other manufacturers.

Software Meets Hardware: the BIOS

A computer motherboard is a piece of hardware: it is the physical circuits and interconnecting wires that forms the backbone of a computer. It has logic circuits which can be manipulated and controlled by the operator, the software program, and input peripherals. But in order to begin operating from a power-off state, a motherboard must be bootstrapped or simply, booted by an initial set of software instructions. Without this vital software, the motherboard is rendered useless.

Most modern motherboard designs use a BIOS, stored in a EEPROM chip soldered to the motherboard, to bootstrap the motherboard. Socketed BIOS chips are widely used, also. By booting the motherboard, the memory, circuitry, and peripherals are tested and configured. This process is known as a Power On Self Test or POST. Errors during POST result in POST error codes, ranging from simple audible beeps from the speaker to complex diagnostic messages displayed on the video monitor.

The BIOS often requires configuration settings to be stored on the motherboard. Since configuration settings must be easily edited, these settings are often stored in non-volatile RAM NVRAM rather than in some sort of read-only memory ROM. When a user makes configuration changes or alters the date and time of the computer, this small NVRAM circuit stores the data. Typically, a small, long-lasting battery e.g. a lithium coin cell CR is used to keep the NVRAM "refreshed" for many years. Therefore, a failing battery on a motherboard will produce the symptoms of a computer that cannot determine the correct date and time, nor remember what hardware configuration the user has selected. The BIOS itself is unaffected by the status of the battery.

Integrated Parts

When IBM first introduced the PC in the s, imitations were quite common. The physical parts which made up the motherboard were trivial to acquire. However, the imitations were never successful until the IBM, ROM ,BIOS was legally copied. To understand why copying the BIOS was an important step, consider that the BIOS contained vital instructions which interacted with peripherals. Without these software instructions in the BIOS, a PC would not function properly. In most modern computer operating systems, the BIOS is bypassed for most hardware functions, but in the s, the BIOS served many vital low-level functions.

So when Compaq Computer Corp. spent US$ million to clone the IBM BIOS using reverse engineering, they became an elite computer manufacturer of IBM PC Clones. Phoenix Technology soon matched their feat and began reselling BIOSes to other clone makers. It has been noted that Microsoft was more than happy to license the operating system DOS, and IBM was more than happy to sue companies that violated the copyright of their BIOS. But by documenting and publicizing the reverse engineering of the BIOS, Compaq and Phoenix were legally competing with IBM using their own copyrighted BIOS.