[sclug] small, quiet things

Alex Butcher lug at assursys.co.uk
Mon Apr 5 13:13:39 UTC 2004

On Mon, 5 Apr 2004, Simon Huggins wrote:
> On Mon, Apr 05, 2004 at 01:26:02AM +0100, Matt wrote:
> > * Simon Heywood <simon at triv.org.uk> [2004-04-04 21:26:39]:
> > > Has anyone here encountered one of these boards?
> > The only problem with these older boards is the "is it a i686 or not"
> > CPU, which means you need to use a distro that doesn't turn on i686
> > instructions.
> I thought the issue was that CMOV was optional in the i686 spec?

Yes, but true i686s (e.g. Intel 686s) have all had the CMOV instruction.


> Debian had an issue with libcrypto but now puts stuff in
> /usr/lib/i686/cmov so it would fall back to the /usr/lib/i586 version on
> the non-supporting platforms.

And, with the exception of the i686.rpms (i.e. openssl, glibc, kernel),
RH/Fedora is compiled with "-march=i386 -mcpu=i686" flags so that the code
is 99.9% optimal for i686 machines, but runs on everything down to the 386.

Unless you know your code benefits greatly from allowing the CMOV
instruction, this is probably the best (i.e. most supportable) way of
compiling code for mass distribution.

> Simon

Best Regards,
Alex Butcher      Brainbench MVP for Internet Security: www.brainbench.com
Bristol, UK                      Need reliable and secure network systems?
PGP/GnuPG ID:0x271fd950                         <http://www.assursys.com/>

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