Re: APM - ACPI

[Russell Coker <russell@coker.com.au>]

On Saturday 21 April 2001 08:52, Drew Parsons wrote:
> > Anybody used ACPI? I've got troubles using apm on a SONY VAIO F801.
> > The processor is AMD K6-III Stepping 4.
>
> As far as I know ACPI or APM is an issue for the motherboard and BIOS,
> rather than strictly depending on the main processor itself.
>
> Anyway, I've been unimpressed enough with ACPI to not bother worrying about
> it for the time being.  I have both ACPI and APM compiled in, but APM gets
> preference, contrary to the documentation.  ACPI can't determine battery
> levels yet.  And worst of all, I couldn't get the suspend function to work
> with ACPI.
>
> In short, I found ACPI basically useless.  But, it's under development, so
> maybe it'll come good sooner or later.  And it's usefulness no doubt varies
> from one system to another.

In APM there is a single action for suspend, the BIOS asks "can I suspend 
now?" and the kernel replies "yes" or "no".  In ACPI the kernel has to go 
through every piece of hardware and put it into suspend separately.  This has 
to be done in order (you can't power down a PCI bus without powering down all 
devices on it).
This makes ACPI much more complex to code (every hardware driver has to be 
changed) which explains why that functionality has not been written yet!

Also FWIW APM functionality seems to have gone backwards for me recently.  In 
recent kernels I have problems with it suspending and not resuming.  
Unfortunately I can't reproduce the problems on demand and haven't been able 
to do much about them.

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