On Mar 9, 2007, at 11:20 AM, Bucky Katz wrote:
>> An ACPI-aware BIOS may have support for loading the state of RAM
>> directly from disk, although the preferred method involves the OS
>> being ACPI-aware and handling the load of RAM from disk itself using
>> the OS-specific device drivers.  The former approach probably
>> requires a dedicated partition which the BIOS uses, whereas the
>> approach using the OS-specific drivers can read and write the state
>> of memory to a file using whatever native filesystem(s) the OS
>> itself supports.
>
> ACPI is great for PCs, but sucks for embedded systems, which rarely,
> if ever, have hardware support for ACPI. It would be nice if a
> framework were able to cope with not relying on ACPI.

You have a good point, but if the firmware/BIOS doesn't support ACPI  
at least to some extent, how is one going to get the system into a S4  
state?  :-)

The older APM standard supports or supported something resembling S1,  
and of course the OS itself can execute HLT in the idle loop until an  
interrupt wakes it up, but in those cases the state of memory is kept  
active, and not flushed to disk.  On the other hand, if someone can  
figure out how to do hibernate-to-disk without ACPI or similar  
support from the firmware, that would be brilliant....

-- 
-Chuck