On Fri, 8 Mar 2002 johan.adolfsson@axis.com wrote:
> What happens if you remove the printf/puts and simply counts the number
> of times the different cases happen?
>
Try it. It doesn't matter. Alan was correct, my computer sucks. However,
they won't give me a 10 GHz one (yet). Note that although gettimeofday()
has 1 microsecond resolution, not all the codes are exercised. We get
something with the granularity of 50 to 190 microseconds. This is
to be expected. You would need a timer that updates at least twice
the expected resolution to be able to exercise all the bits, i.e.,
something with a 2 MHz update-rate, that could be read before it
changed, or a real 'buzzer' of an ISR at 2 MHz. Before everybody
argues, a 1 MHz ISR would give you a value that is updated at
1 microsecond intervals, but now we have to read in asynchronously
and that's where Shannon (information theory) laws take effect.
> Another thought: Isn't it quite common that clock generators has a mode
> where the frequency differs around the desired frequency to spread the
> spectrum
> and easier pass EMC tests?
Actually, I think they just use a junk piezo-resonator instead of a
quartz crystal. If you try spread-spectrum with a bus-clock, you will
screw up all the timing so the bus won't work. Think PCI Bus with its
'reflected-wave' mechanism. If the clock timimg was to change during
PCI Bus activity, all bets are off.
> Could that be the case with the laptop?
> /Johan
>
Don't think so.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Bill Gates? Who?
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This archive was generated by hypermail 2b29 : Fri Mar 15 2002 - 22:00:09 EST