This chip looks after the basic input/output connectors at the rear of the motherboard, such as the keyboard port, mouse port, joystick ports, serial port and printer port.  It can handle the wake-up on keyboard/mouse function.  It also, supports legacy interfaces like a floppy disk controller.

You'll notice the various cooling fan connectors on the board.  This chip can control the speed and monitor those fans.  In the event of a fan failing, the chip can signal the system to alert the user to the problem.  The exact functions can be re-configured, as needed, in the BIOS.

This particular Winbond chip features an ACPI controller for system power management.

Useful external link

www.winbond-usa.com