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SubjectRe: Requested FAQ addition - Mandrake and partial-i686 platforms
On Tue, Aug 12, 2003 at 10:48:59AM -0400, Brandon Stewart wrote:
> Apparently, there is an issue with glibc on versions less than 2.3.1-15
> (and maybe others), where it mistakenly treats CPUs as full i686
> compliant when they only execute a subset of the i686 instructions. For
> example, the VIA C3 supports pretty much everything i686 except CMOV,
> yet the broken versions of glibc will detect it as fully i686 compliant.

It's actually a problem that gcc assumes 686 = 686+cmov. The glibc
isn't broken, its just compiled for gcc's view of what 686 is.

> From someone who emailed me privately, this apparently affects K6-III
> as well. Possibly other Cyrix or AMD CPUs are affected, though I don't
> have a complete list.

No. K6-III is a family 5 processor, so should get built for 586.

> There are three possible workarounds:
> 1) Upgrade glibc to a working version. I haven't done this myself, so I
> don't know if the bug has been fixed yet. But it would be the best solution.

Its not a glibc bug.

> 2) Remove i686 libraries from glibc. This can be done by 'mv /lib/i686
> /lib/i686.invalid'. This is what I did, and it works. While some
> performance is lost, it's not noticeable, especially given that the
> stock Mandrake kernel is i386 compatible, and so has limited optimization.

This is the best of the bunch, and is the same solution debian users
were using for some time a while back when someone made a '686' version
of libssl.

Dave

--
Dave Jones http://www.codemonkey.org.uk
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