Bootstrapping using the Basic input output
Bootstrapping using the Basic input output system
Motherboards contain some non-volatile memory to initialize the system and load some startup software, usually an operating system, from some external peripheral device. Microcomputers such as the Apple II and IBM PC used ROM chips mounted in sockets on the motherboard. At power-up, the central processor would load its program counter with the address of the boot ROM and start executing instructions from the ROM. These instructions initialized and tested the system hardware, displayed system information on the screen, performed RAM checks, and then loaded an initial program from an external or peripheral device. If none was available, then the computer would perform tasks from other memory stores or display an error message, depending on the model and design of the computer and the ROM version. For example, both the Apple II and the original IBM PC had Microsoft Cassette BASIC in ROM and would start that if no program could be loaded from disk.
Most modern motherboard designs use a BIOS, stored in an EEPROM chip soldered to or socketed on the motherboard, to booting an operating system. Non-operating system boot programs are still supported on modern IBM PC-descended machines, but nowadays it is assumed that the boot program will be a complex operating system such as Microsoft Windows or Linux. When power is first supplied to the motherboard, the BIOS firmware tests and configures memory, circuitry, and peripherals. This Power-On Self Test (POST) may include testing some of the following things:
Cards inserted into slots, such as conventional PCI
Temperatures, voltages, and fan speeds for hardware monitoring
CMOS used to store BIOS setup configuration
Keyboard and Mouse
Optical drives: CD-ROM or DVD-ROM
SCSI hard drive
IDE, EIDE, or Serial ATA Hard disk drive
Security devices, such as a fingerprint reader or the state of a latching switch to detect intrusion
USB devices, such as a memory storage device
On recent motherboards the BIOS may also patch the central processor microcode if the BIOS detects that the installed CPU is one for which errata have been published.
Air pollution and reliability
High rates of motherboard failures in China and India appear to be due to "sulfurous air pollution produced by coal" that's burned to generate electricity. Air pollution corrodes the circuitry, according to Intel researchers.