[mythtv-users] Scheduled wakeup acpi-alarm vs nvram-wakeup

mike choy mike at acaciaclose.co.uk
Fri Dec 30 07:24:47 EST 2005

Hi Team

I wonder if its time to revisit ACPI for doing scheduled wakeups. This looks much more elegant to me,
and seems to have made real progress in 2.6.14 kernels. 
This will off course need a Mother board and BIOS that supports the Real Time Clock alarm function
but as this is exposed via the OS, then this looks much safer than poking directly into NVRAM.
( most BIOS have alarms that go upto 1 month ahead, some older ones also only have 1 day ahead)!

I am using SUSE 10.0 but would be interested if other distros now have good ACPI support
Here is a quick link to the ACPI documentation from Novell, and the acpi4linux home page

Here are the results for my system
Read the RTC alarm clock
> cat /proc/acpi
> cat /proc/acpi/alarm
2005-12-00 10:11:33

Now check we can write a value back into the BIOS
Login as root
#echo 2005-12-31 10:30:00 >/proc/acpi/alarm

Now check it worked
#cat /proc/acpi
2005-12-31 10:30:00

#shutdown -h now

Note you will NOT see this change the wake up time in the BIOS
And wait for the system to spin up.

Now going away to see how to integrate to Myth

Mike C

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