Super I/O

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Diagram of a motherboard, which supports many on-board peripheral functions as well as several expansion slots.

Super I/O is a class of I/O controller integrated circuits that began to be used on personal computer motherboards in the late 1980s, originally as add-in cards, later embedded on the motherboards. A super I/O chip combines interfaces for a variety of low-bandwidth devices. The functions below are usually provided by the super I/O if they are on the motherboard:

By combining many functions in a single chip, the number of parts needed on a motherboard is reduced, thus reducing the cost of production.

Some chips have support to detect if the case gets opened (chassis intrusion).

The original super I/O chips communicated with the central processing unit via a connection with an Industry Standard Architecture (ISA) bus. With the evolution away from ISA towards use of the Peripheral Component Interconnect (PCI) bus, the Super I/O chip was often the biggest remaining reason for continuing inclusion of ISA on the motherboard.

Modern super I/O chips use the Low Pin Count (LPC) bus instead of ISA for communication with the Central processing unit. This normally occurs through an LPC interface on the southbridge chip of the motherboard.

Companies that make super I/O controllers include Nuvoton, ITE, Fintek, and Microchip Technology. National Semiconductor used to make super I/O controllers but sold that business to Winbond, which already had a competing super I/O controller business, in 2005. Winbond then spun off its logic businesses to a wholly owned subsidiary, Nuvoton. SMSC made Super I/O chips and then got acquired by Microchip Technology.

ITE Super I/O chip
Smsc Super I/O chip on IBM motherboard

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