Messages in this thread | | | Date | Fri, 21 Nov 2003 06:46:44 +1100 | From | Anton Blanchard <> | Subject | Re: high res timestamps and SMP |
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Hi,
> Last time I checked, all 32-bit PowerPC chips ran that clock at 1/4 > of the bus clock speed.
It depends on the chip, on recent ppc64 boxes its 1/8 of the processor clock speed.
> That may be adequate for time-of-day and I/O delays and such, but > it's worthless for timestamps or performance measurements.
Can you show me the application that depends on timestamps being that accurate?
Running the multiplier at a set fraction of the processor speed is a good idea I think. Go look at any large x86 box (and possibly ia64 box) and you will find the timebases are not synced. Even our biggest box has the timebase synced, its easy to do when the timebase is running at a reasonable rate.
In a trade off between unsynced timebases and timebase running at a fraction of the cpu speed, ill take the latter :) (Ask the x86 guys what a pain unsynced timebases are)
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