Re: KDE compiled for i686
> I know that from 386 upto early pentiums there were some basic
> additions to the instruction set so re-compiling should get a bit
> better performance because gcc can select faster instructions.
>
about every new generation of processors brought a few new instructions/
instruction classes. the p2-series have most notably conditional moves,
which gcc can use.
> But I thought that to take advantage of MXX and PIII's
> floating-point MMX instructions would take specifically written code
> to see any kind of improvement.
>
yes, when you want to use these highly specialized instructions, you should
use libraries, which are hand-written in assembler.
> Can/Does gcc optimise for use of the MMX and other 3D-type
> instructions?
>
no, afaik.
> I would have thought that with the ridiculous clock speeds in use
> now that the minor increases gained by compiling for Pentium-level
> over 1386 would then be lost in memory-access times. Would my two
> PII 350's get noticeably better performance on a 100Mhz Memory bus
> if I recompiled my system?
>
you can expect to get no noticable speed gain. the executables become
a tiny bit smaller (because of the conditional moves, etc.), but this
is mostly negligible, too.
imo, it's not worth the effort unless you don't want to use packages
at all.
you should do this only for very time-critical programs, but not for
a whole desktop.
> As far as compiling, is it fairly easy to compile source-deb's?
>
yes, see the other mails.
best regards
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