Most current PCs offer the possibility of automatic wakeup. A certain wakeup time, typically within one month in the future, can be set up from within the BIOS. At this time the PC will restart automatically, as long as it has been shut down by the APM poweroff function (and the power has not been turned off). Usually, only the day of month and the HH:MM:SS time of day can be set for a future wakeup.

wakeup_clock is a tool to set up this date and time from the running system, such that a specific downtime can be scheduled without having to turn the system back on manually. During the downtime, only the standby power of the ATX power supply is consumed.

Unfortunately, there is absolutely no standard which CMOS registers need to be set up to achieve automatic wakeup, each mainboard vendor has implemented this differently.

Note: Just turning the PC off manually will normally not work, it has to be shut down by the APM or (preferably, and on some boards necessarily) the ACPI poweroff function.

Supported boards and systems

• ASUS P5A and P2B
• ASUS A7V8X (thanks Calvin Harrigan)
• ASUS P4SGX (thanks Andy Simpson)
• ECS K7VZA and K7S5A (the latter now with fixed checksum computation..)
• MSI 6119
• MSI K7T Turbo 2 Model # MS-6330 (thanks Calvin Harrigan)
• ASRock K7VT2
• ASRock K7VT6
• ASRock K7S8X
• ABIT IS7-E2 (thanks Magnus Sandin)
• VIA EPIA M10000
• MSI K8T Neo-V
• Gigabyte 8i945GMF (New! thanks B. Remond)
• ASRock ConRoe945G (New!)

I'm compiling and running wakeup_clock on ix86-Linux only, however apart from the cmos_..() routines (which use outb()) and the reading of the /dev/mem special file to identify the board, there is nothing that would prevent a port to other systems. Patches are always welcome.

Please note that wakeup_clock always must be run as root. On some boards, it is required to run with ACPI enabled (e.g. I had to boot with acpi=force for the MSI K8T Neo-V). In some particular cases, after running wakeup_clock it is unfortunately necessary to complete a reboot cycle before the changed wakeup time actually takes effect.

Usage

Usage  : wakeup_clock [date_string]
  note : date_string interpreted in local time
Example: wakeup_clock "4/5 14:15"

wakeup_clock takes a single argument, a date string. This string must be in a format understood by the date program, and usually needs to be quoted to prevent the shell from creating multiple arguments. In the example above, the wakeup time would be April 5th at 2:15 pm.

Using the date program has the advantage of extensive parsing capabilities, and that the time can be specified in the local time zone. wakeup_clock automatically detects (via the third line of the /etc/adjtime file) whether the BIOS clock is set to UTC (like it should be!) and computes the proper BIOS time which is eventually written to the board-specific CMOS registers.

Note that wakeup_clock currently does not activate the "automatic wakeup" feature (you have to do that yourself in the BIOS once), it only sets the date and time at which an automatic wakeup will occur if enabled. There are also no sanity checks whether the specified time is actually in the future, and less than a month in the future; the month is simply not used.

How to add support for a new board

wakeup_clock -d >d10

wakeup_clock -d >d11

diff d1 d2

Be careful when experimenting with the CMOS registers. Setting the wrong registers randomly might cause instability and necessitate a clearing of the CMOS in hardware!

Finally, a string in the BIOS needs to be found (e.g. from the boot screen) that uniquely identifies the mainboard. This string can then be looked for in the output of

dd if=/dev/mem bs=1 skip=983040 count=256000

Please send information and patches to the address below. Thanks.

Source code for wakeup_clock

gcc -O wakeup_clock.c -o wakeup_clock

License