timecounter and Hz quality in kern RELENG_6

[Michael Schuh]

Hello,

i be very surprised about the performance of RELENG_6.
Congratulations to the entire Team for this very good work.

Now i have 2 Machines installed with 6.0-RC1, and i have seen that on
both machines the Hz is differntly with GENERIC-Kernel.
Machine A is an Sempron 2400+ that runs as 2500+
(i have tuned the clock to best RAM-Performace)
Machine B is an Duron 700MHz

On Machine A i got an Hz from 2000 effectively
systat -vmstat 1 show me 2000 IRQ/s on clk
sysctl say's 1000....i think, but not sure

On Machine B i got an Hz from 1000 effectively
systat-vmstat 1 show me 1000 IRQ/s on clk

After digging in the source i have found that timec.c have an routine for
computing the so called "Hz quality".

Can anyone explain me the "mystics" behind Hz quality,
and why or how this quality is computed and what are the
efforts?

My knowledge is not deep enough to know these details.

thanks

best regards

michael