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Date: Tue, 20 Jul 2010 12:54:55 +0200
From: Marius Strobl <marius@alchemy.franken.de>
To: Alexander Motin <mav@FreeBSD.org>
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Cc: freebsd-sparc64@FreeBSD.org
Subject: Re: [RFC] Event timers on sparc64/sun4v
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On Mon, Jul 19, 2010 at 06:03:40PM +0300, Alexander Motin wrote:
> 
> There is indeed too small info about this. I've found that thing about
> edge, you've noticed, also I've found that TICK clock is integer
> multiply of STICK. Taking analogy to x86 I may assume that CPUs with
> different frequencies still quite likely use same bus frequency (STICK),
> or even sharing the same bus, while have different multipliers for core
> (TICK) frequency.
> It is indeed only an assumption, but it would be strange for CPU
> designers to implement one more counter, which is not better then
> already existing one.

My understanding is that the only advantage of the STICK counter
over the TICK one is that the former is always driven by the same
frequency across all CPUs in a system, regardless of the frequency
the CPUs are running at (as needed in machines equipped with
different CPU models or when down throttling).

Marius