Abstract: A point-to-point serial communication link between a system interface unit and a peripheral bus interface unit is provide. The system bus interface unit may interface between a CPU bus and a peripheral bus, such as the PCI bus, and may be referred to as a north bridge. The system interface unit may also interface to main memory and to an advanced graphics port. The peripheral bus interface unit may interface between a first peripheral bus, such as the PCI bus, and a second peripheral bus, such as an ISA bus, and may be referred to as a south bridge. The serial communication link between the system interface unit and the bus interface unit may be a one wire serial bus that uses a bus clock from the first peripheral bus as a timing reference. This clock may be the PCI clock. The serial communication link may use a single pin on the system interface unit and a single pin on the bus interface unit to transfer commands between the interface units.

Abstract: An advanced configuration and power interface operating system transparent method to control the wake-to-sleep and sleep-to-wake transitions includes: detecting a sleep enable command; temporarily blocking completion of the sleep enable command; generating an interrupt; configuring an input-output device; and completing the sleep enable command. The sleep enable command can be a write command to an advanced configuration and power interface sleep enable data storage unit. The generated interrupt can be a system management interrupt that invokes a basic input-output device configuration program.