Re: TSC vs. HPET timecounter priority

[Erik Fair <fair%netbsd.org@localhost>]

On Aug 13, 2012, at 08:49, Jukka Ruohonen wrote:

> On Sun, Aug 12, 2012 at 08:14:50PM -0700, Erik Fair wrote:
>> NetBSD has a problem with NTP time keeping on x86 systems which have TSC:
>> if those systems have variable CPU clock frequency support for power
>> consumption efficiency (e.g.  SpeedStep, PowerNow), if or when the CPU
>> frequency changes, the relationship between TSC and the ticking of real
>> time changes.  That screws up any kind of interval time & frequency
>> measurement one is using TSC for.
> 
> I think this is no longer true with new AMD and Intel processors.

Can you find a reference in either Intel or AMD's documentation, and to which 
CPUs that applies (preferably with some indicator we can test at system 
initialization time)?

        thanks,

        Erik <fair%clock.org@localhost>