When a USB device is enabled to wake the computer, the default behavior permits the computer to enter the S1 system power state for standby. Standby is not the S3 system power state. The S1 system power state is a "lighter" system power state than S3. The S1 system power state typically conserves less power than the S3 system power state.
By using the following registry entry, you can override entering the S1 system power state as a default behavior when a USB device is enabled to wake the computer:
The basic input/output system (BIOS) reports the wake capabilities of an on-board device, such as a USB host controller. Some systems report that "wake" from the S3 system power state for their on-board USB host controller is supported. However, problems may occur when these other systems try to use wake from the S3 system power state for their on-board USB host controller. These problems include the following:
- Loss of power during the S3 system power state on the USB
- False device removal and false arrival notifications upon resume from standby
- Reset of attached USB devices during suspend and resume
- Failure to resume fully from the S3 system power state
Note Values other than 0x00000000 for USBBIOSx are reserved for future use. Do not use values other than 0x00000000 for USBBIOSx.
The USBBIOSx registry value is applied globally to all USB host controllers in the system. The BIOS reports the wake capabilities of all attached USB host controllers.
Installation of a third-party add-in USB host controller card when the USBBIOSx value is set to 0x00000000 may cause problems with waking the computer through that controller.
Note Another similar USB-specific registry value that is named USBBIOSHacks is unsupported and must not be used.
The USBBIOSx registry value is intended for use by computer manufacturers when they pre-install Windows XP or Windows Server 2003 on their computers. We do not recommend that end-users set this registry value. We do not recommend that USB hardware vendors try to set this value during installation of their USB device.
Note By default, the USBBIOSx value may not exist in the registry. In this case, you must manually add this value.