Does FBSD support 'software suspend' ?

[Kevin Oberman]

> Hello,
>            Does FBSD support 'software suspend' like linux does ?
> Also,from the archives i come to know that FBSD supports
> 'suspend to disk'.What is the exact difference between the two ?
> or are they one and the same ?

FreeBSD tries to support both. They are more technically referred to as S3 and 
S4 states but are more typically called "suspend to RAM" and "suspend to disk" 
respectively. The terms "suspend" and "hibernate" are also used.

S3 halts the CPU and disk drives, shuts down the video and turns off the 
display. It tries to either turn off  peripherals or place in limited power 
mode. This should reduce power consumption dramatically, but RAM is kept alive 
as are some other parts of system.

S4 writes RAM and some added system information to a specially designated 
partition on the disk and completely shuts off the system. It takes longer to 
resume and requires a bit more disk space than the size of RAM.

Because of the huge number of differences in laptops, some simply don't work. 
This is something that is being worked on constantly, but new laptops and 
modified BIOSes are always showing up and causing problems. FreeBSD 5 and 6 
support these functions through ACPI. All versions since 4 support APM. APM is 
an older power management system and some newer laptops don't support it, but, 
when available, it's more likely to work as most of the process is handled in 
BIOS. ACPI is vastly more powerful than APM, but relies on software to do more 
of the work, so is more prone to problems.

FWIW, my T30 does S3 pretty well. Last I checked, the only issue was that my 
audio was broken ofter the system resumed. I have never tried S4 as I never 
had a free slice (partition to Windows) to dedicate to it.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634