Rik van Riel wrote:
>
> On Fri, 29 Jan 1999, Neil Conway wrote:
>
> > The behaviour is equally likely to change if I run the code under bash
> > instead of tcsh - sometimes bash runs it quicker (and REPEATABLY QUICKER
> > I mean, not once) and sometimes tcsh runs it quicker. The behaviour
> > stays the same for a while until something in the innards of the machine
> > (memory-mapping?) changes and then the speed-changing can either invert
> > polarity or disappear for a while... Quite often when it disappears I'm
> > left with repeated runs giving me the LOWER speed which is a shame.
>
> As Richard said, it's most probably cache line aliasing.
>
> This severely bites me too. On my UP Pentium 100 w/
> Triton chipset x11amp used to use 35 to 40% of the
> CPU. On my dual P120 w/ Neptune chipset the CPU usage
> varies between 60 and 95%.
>
> The huge increase probably comes from the facts that
> x11amp is switching CPU too often and the more
> primitive L2 cache mapping on Neptune boards.
Well CPU switching doesn't explain my observations as I have lots of
instances of seeing it on UP machines.
Dunno about the cache issues - to be honest I don't know why different
page layouts in physical RAM makes such a big difference...
Neil
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