John Baldwin wrote:

quoted text
> On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote:

>> I'm seeing similar results.

>>

>> [root@orangebox /usr/home/gcooper]# dmesg | grep 'Timecounter "'

>> Timecounter "i8254" frequency 1193182 Hz quality 0

>> Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000

>> Timecounter "HPET" frequency 14318180 Hz quality 900

>> [root@orangebox /usr/home/gcooper]# ./cgt

>> 1369355

>> [root@orangebox /usr/home/gcooper]# sysctl

>> kern.timecounter.hardware="ACPI-fast"

>> kern.timecounter.hardware: HPET -> ACPI-fast

>> [root@orangebox /usr/home/gcooper]# ./cgt

>> 772289

>>

>> Why's the default ACPI-fast? For power-saving functionality or because

>> of the `quality' factor? What is the criteria that determines the

>> `quality' of a clock as what's being reported above (I know what

>> determines the quality of a clock visually from a oscilloscope =])?

>

> I suspect that the quality of the HPET driver is lower simply because no one

> had measured it previously and HPET is newer and less "proven".

> 

 From memory, HPET was massively slower on some of the AMD test hardware

I was using.  There was a thread about it on one of the mailing lists,

but I can't find it right now.
Kris

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