Laptop And ACPI

[Nate Lawson]

Bruno Ducrot wrote:
> On Tue, Mar 01, 2005 at 03:03:40AM -0000, Joe Holden wrote:
> 
>>Hi, i'm having issues with a 4 year or so old laptop, if I disable acpi, the
>>CPU is reported at 168 MHz and the clock tends to jump about abit.
>>
>>
>>It's a Pentium 3 650 MHz
> 
> 
> The TSC of PIII is more or less broken if using speedstep or apm idle
> call.  Its also unreliable when the processor is going to SMM (which
> happens often IIRC on laptops when APM is enabled)
> 
> With ACPI, FreeBSD use another time counter (acpi_timer) by
> default and not TSC so you don't have this issue.
> 
> You should use another time counter (its in a FAQ IIRC).
> 
> Example:
> 
> root at poupon.echo-net.net [8:47] ~# sysctl kern.timecounter.choice
> kern.timecounter.choice: TSC(800) ACPI-fast(1000) i8254(0) dummy(-1000000)
> root at poupon.echo-net.net [8:47] ~# sysctl kern.timecounter.hardware=i8254
> 
> If i8254 is correct, then use it.

Thanks, Bruno.  Just another note that you should be able to put the 
timecounter choice in /boot/loader.conf too I think.

-- 
Nate