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From: Simon Wright <simon@pushface.org>
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Subject: Re: Any leap year issues caused by Ada yesterday?
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Date: 2012-03-06T09:20:55+00:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> If you set the timer at 1ms rate, you would have 1ms delays. The
> problem is that the time stamps would have only 1ms accuracy! For
> 10kHz measurements and control we are doing, this is a bit dire. So we
> are setting the timer interrupts at 0.01ms (which is our humble
> contribution to the "man-made" climate change (:-))

Our (VxWorks) solution was to use the PowerPC timebase register; at each
clock tick, store the Ada clock and the current tb; in between, use the
tb to interpolate. On the hardware we were using, that gave us 40 ns
resolution (a microsecond would have been fine!)

I couldn't show you that code even if I still had access, it's
proprietary, but there's something at [1].

An Intel equivalent used to work, but (a) most OSs give microsecond
resolution anyway, (b) it certainly doesn't work on Mac OS X with dual
cores where the core is slowed right down if it has nothing to do! (my
interpretation of the observed behaviour).

[1] http://booch95.svn.sourceforge.net/viewvc/booch95/trunk/src/bc-support-high_resolution_time-clock.adb-ppc32?revision=1415&view=markup