Invalid detection CPU frequency ?

Nate Lawson nate at
Tue Sep 27 16:35:07 PDT 2005

Vladimir Grebenschikov wrote:
> It looks strange but sometimes my notebook start on full-speed (1.7GHz)
> and sysctls output looks like:
> dev.cpu.0.freq: 1687
> dev.cpu.0.freq_levels: 1687/-1 1476/-1 1265/-1 1054/-1 843/-1 632/-1 421/-1 210/-1
> dev.acpi_throttle.0.%desc: ACPI CPU Throttling
> And sometimes it starts on low speed (~500 Mhz)
> dev.cpu.0.freq: 595
> dev.cpu.0.freq_levels: 595/-1 520/-1 446/-1 371/-1 297/-1 223/-1 148/-1 74/-1
> dev.acpi_throttle.0.%desc: ACPI CPU Throttling

> And speed can't be raised by powerd or other.
> Looks like it happens when notebook stats or shutdowns on batteries.
> Rebooting on AC power cures situation. But anyway - I do not think it is normal.
> Any suggestions ? 

It's very simple.  You have an old notebook that only supports 
throttling, not SpeedStep or other options.  Your BIOS sets the initial 
speed based on AC line status on boot.  If you look at your CPU 
announcement at the top of dmesg, it will show 595 Mhz or whatever since 
it uses a simple calibration loop.

I might consider always setting 100% in the attach routine for 
acpi_throttle and p4tcc to get proper probe values.  You'll still have a 
problem if you use the TSC timecounter since it's only calibrated at boot.


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