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Re: default CPU target for ix86 based ports

On Wed, 2003-08-06 10:05:13 +0200, Matthias Klose <doko@cs.tu-berlin.de>
wrote in message <[🔎] 16176.46777.785177.447483@gargle.gargle.HOWL>:
> Now that the kernel-image packages supports hw emulation of i486
> instructions on i386 hardware, I'd like to change the code generation
> to default to i486 (not sure if it should be tuned for any other
> target, i.e. -mtune=i686).


I'm using (well, mostly for testing) some i386 class machines and it's
even today a pain to test bleeding edge software at all.

Yes, there's a i486 emulator, but that hasn't been ported to 2.6.x. I've
tried a fast port to that, but it Oopses now instead if sending a

So... (Using a vanilla kernel, ) libstdc++5 already rendered i386 to
being quite unuseable (heck, apt-get as Debian's most important
application doesn't any longer work!) I've had (on lkml, I think) some
email exchange with the original emulator author. He expressed that he
wouldn't fully rely on that beast - it's a hack.

Having a "broken" libstdc++ is already bad enough. Please, please please
please please don't make it worse as it's already today. I heared rumors
that gcc-3.4 might fix the current situation (wrt. libstdc++).

...and up to now, I haven't seen real hard numbers that show that
optimizing for i486 does really make anything noticeable faster. From my
point of view, you're making something marginally (at best...) faster
but giving up i386 compatibility (relying on a hackish emulator which
isn't right now available for the latest kernel).

At least, Debian still calls this architecture "x68", "ix86" and "i386"
(cf. http://www.debian.org/ports/) which __includes__ original i386 in
my reading.

Maybe we'd go another way and build two distributions - i386 as well as
i486 or i586. I bet there are still i386 machines out there, but they're
not updated that often. Please don't cut their update pathes...


   Jan-Benedict Glaw       jbglaw@lug-owl.de    . +49-172-7608481
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