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Super I/O Controller Functions

The Super I/O controller is a single chip that, much like the system chipset, performs many functions that used to take several pieces of hardware in the past. This standardizes and simplifies the design, and thus reduces cost. The Super I/O chip typically is responsible for controlling the slower-speed, mundane peripherals found in every PC. Since these devices have been mostly standardized, they are virtually the same on every PC and it is easier to integrate these into a commodity chip instead of worrying about them for each motherboard design.

The major functions of the Super I/O controller chip are:

• Serial Port Control: The Super I/O chip controls the serial ports and includes the UARTs that make the ports function. Almost all modern chips provide the high-performance 16550A UART, which includes a 16-byte FIFO buffer.
• Parallel Port Control: The Super I/O chip provides the circuitry to drive the parallel port. This includes support for the newer parallel port types such as EPP and ECP.
• Floppy Disk Drive Control: Support for floppy disk drives is provided by the super I/O chip. Newer models support the higher 1.0 MB/sec transfer rate, and provide support for 2.88 MB floppy drives, although these never did catch on. Floppy-based tape drives also use the same interface; see here for more on the floppy controller and floppy interface.

Newer PCs sometimes integrate the functions even more, and include in the Super I/O chip not only the functions above but also the real-time clock, keyboard controller, and in some cases even the IDE hard disk controllers. It is far more common to find IDE controllers implement through the system chipset, however, especially in newer systems.

National Semiconductor makes a large number of these chips, and they can sometimes be identified by looking for their name or logo on the surface of the chip.

Note: On older PCs there is no super I/O controller chip; the interfaces to the serial and parallel ports, and the floppy disk drives, are provided by an I/O controller card (which often also controlled the hard disk drives).

Next: Additional Integrated Motherboard Functions

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