Fan Control Success on IBM T40? (another quick Q)

[Nate Lawson]

On Wed, 28 Apr 2004, Nate Lawson wrote:
> On Wed, 28 Apr 2004, Jeffrey Katcher wrote:
> > >From everything I've seen (on the linux-acpi lists), the T40 doesn't have _any_
> > fan control in the DSDT.  Apparently it's explicitly controlled via SMBIOS.
> > There's a SMAPI interface available from FreeBSD, but I don't have enough info
> > yet to exploit it.
>
> > Second question, still on power/clock issues, but diverging a little from ACPI:
> > What's the interaction between SpeedStep clock and ACPI clock percentage?
> > If I start on batteries, apparently the clock is at 600Mhz (even though dmesg
> > reports it as 1600Mhz no matter what).  ACPI CPU then can reduce this base by
> > eighths?  So if I start on AC, it's eighths of 1600 and DC, it's eighths of
> > 600?
>

I forgot to add -- the reason the clock rate announced at boot time is
different is because the test for CPU TSC is done before acpi is enabled.
At some point when the SMI is disabled and acpi enabled, the clock rate is
switched by your BIOS to the lower rate.  You can see this because the
clock rate announced by the TSC timecounter will be ~600 mhz while the
initial boot clock rate will list ~1600 mhz.

-Nate