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Re: CVS commit: src/sys/arch/x86/x86

On Mon, 8 Aug 2011, Jukka Ruohonen wrote:
Yes, but when possible, we should always prefer actual, reliable, CPU
information instead of the BIOS. Note also that at least with Intel CPUs,
the TSC should be entirely safe with the current stock-NetBSD (i.e. no
automatic CPU power management), but now you've marked it unreliable for
many systems (cf. also [1]).

It's not just Cx states but also MP synchronization (remember TSC is per-CPU). There are reports of 'WARNING: negative runtime; monotonic clock has gone backwards' messages using TSC on MP systems, which this will fix if the flag is set. Newer systems with invariant TSC shouldn't set the USE_PLATFORM_CLOCK flag.

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