On Wed, Jul 11, 2007 at 09:54:19PM +0900, Izumi Tsutsui wrote:
> pavel@NetBSD.org wrote:
> 
> > I notice it periodically synces the local cycle counters.  Is it really
> > needed? I think Alpha motherboard have a central clock which drives the
> > CPUs, so they are always precisely syncronized and this shouldn't be
> > needed.
> 
> If each CPU has PLL to multiply base clock, each PLL has
> an internal oscillator which is controlled by comparing against
> base clock with feedback loop. They are almost syncronized but
> not precisely, so could have a few tolerance, I think.

What would be the maximum difference?

> Anyway, current kern_microtime.c based code also has the similar
> sync code in the clock interrupt. (see alpha/interrupt.c)

Sure, this comment applies also to current situation. It would be
interesting to disable the synchronization in the current code and see if
it makes any difference.

Pavel