Methods and apparatus for providing a bus interface are disclosed. An example method for providing a bus interface includes operating first circuitry using a first power supply voltage in a normal operating mode, where the first circuitry includes at least a portion of datapath circuitry of the bus interface. The example method further includes powering down the first circuitry in a low power operating mode and operating second circuitry using the first power supply voltage in the normal operating mode. The example method also includes operating the second circuitry using a second power supply voltage in the low power operating mode. The second circuitry includes a power management control circuit adapted to receive a power management event indication signal. Responsive to the power management event indication signal, the control circuit provides at least one of an in-band power management indication and an out-of-band power management indication to one or more devices in a computing system. In the example method, the first and second power supply voltages may be provided by a single power supply or, alternatively, by multiple power supplies.