Re: calcru: runtime went backwards

From: Poul-Henning Kamp <phk_at_phk.freebsd.dk>
Date: Sun, 12 Feb 2006 21:59:01 +0000
In message <20060212225911.M598_at_free.home.local>, Yuriy Tsibizov writes:


>> The other side of this is that I've been looking at having the
>> ACPI power management code announce the maximum speed of the TSC
>> to the cputick code, that would make such machines "fixed frequency"
>> cpu_tick machines from the start and even if enabled, this warning
>> should not issue in that case.

>I have CPU (AMD K6) with TSC, but my motherboard (ASUS TX97) does not 
>support ACPI. This combination can also be treated as a "fixed frequency" 
>machine.

The trouble really is that there is no way to tell if the TSC is fixed
frequency.  Some of the machines where it is variable can tell us
that it is variable (ie: ACPI is enabled) and some subset of those
may be able to tell what the max is and this effectively make it
fixed.

For a fixed machine which is treated as variable, what will happen
is that the 16 second calibration will keep finding close to the
same number.

Every so often however, a slightly higher number will be found and
then this message may occur...

As I said: I may simply hide the message for for machines with
variable cpu_tick (even if it is in reality fixed).

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk_at_FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.
Received on Sun Feb 12 2006 - 20:59:08 UTC

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