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Re: AMD K6-2 identified as i586?



Thanks everyone, Adam and JFM,

- was on the verge of trying the i686 rpm install for
the new NVIDIA (build 4191) rpm. Guess i'll hold off
on that.
 
That's interesting about the i386 rpm versions. JFM,
Your're saying test replacing a i586 rpm with an i386?
Ok I'll try it but still have a lot to learn. Still
pretty much a newbie with linux/unix compiling (being
a COBOL/mainframe person for years though, these
concepts are not totally out reach :^>  )

j.ingersoll

On Sun, 2002-12-15 at 00:43, Mr. Adam ALLEN wrote:
> I remember back in the day when AMD-K6-3 was a new
processor it was
> marketed as better performing than an equivalent
Intel PII - however it
> is classified as an i586- so i686 RPM's are not a
good idea. 
> 

The K6 family does NOT support some instructions of
the Pentium Pro
and later processors (except for the Pentium MMX) so
if you use 686
binaries on a K6 they will crash.

> As far as I remember there is a "k6" optimisation
when compiling, though
> how much difference there is between i586 and k6 and
i686 is one for
> debate by those who care and understand more than I
do.
> 
> > My concern is with installing RPMs optimized for
i686,
> > whether this will cause any problems. 
> > 
> > Up until now, I've always stuck with those
optimized
> > for i386 (i.e. generic) or i586.
> > 
> 

The 386 RPMs are not optimized for the 386.  They are
optimized for the
PII/PIII/Celeron family ie when deciding how to
generate code Gcc bases
on the 686 timetable. It just doesn't use the whole
instruction set.
686 RPMs are compiled with the whole instruction set
but on most
programs this brings only minimal improvements
respective to
programs optimized for the 686 buyt with 386
instructions.  Thus only
when there are processor-specific parts written in
assembler (whose use
impedes running on  a lesser procesor) does it make
sense to compile for
i686.

My experience is that the K6 family gets very good
performance from binaries optimized for the 686 (with
386 instructions) like those you get with Redhat,
nearly as good as when optimiezd specifically for the
K6 , quite better than when optimized for the 386 and
_far_ better than when optiized for the Pentium (even
with whole instruction set), so you could test
replacing your 586 RPMS by the 386 versions.  YMMV
because there are assmebler parts in those RPMs

			JFM


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