CentOS 5 i586 support

Introduction

CentOS is still used on i586 CPUs and VIA C3 CPUs (which are i686 CPUs, but do not have a cmov instruction). Our goals is to support i586-class CPUs on CentOS 5. This page describes the progress of i586 support.

Testing

You can help testing in with the following hardware:

• Real i586 hardware (with enough memory).
• VIA C3-based (pre-Nehemiah) CPUs.

• qemu without handling of cmov instructions. This is handy for quick testing, because you can install the i686 version of CentOS 5 with an unpatched qemu, and then test with a patched qemu. Patch: qemu-0.9.0-no-cmov.diff

Status

CentOS 5 currently boots on at least cmov-less i686 CPUs with the following changes (please add confirmation for i586 and VIA C3 CPUs):

• The i586 CentOS Plus (testing) kernel.
• Replacement of glibc.i686 with glibc.i386.
• Replacement of openssl.i686 with openssl.i386.

-ffast-math

Some i386 packages don't work, because they introduce cmov instructions through the -ffast-math gcc parameter. Some packages using -ffast-math seem not to call cmov instructions, others using it do. The following packages have -ffast-math in their build logs:

Not Affected

• libao-0.8.6-5 (not affected?)
• libdbi-0.8.1-2.1 (not affected?)
• libdbi-drivers-0.8.1a-1.2.2 (not affected?)
• libogg-1.1.3-3 (not affected?)
• libvorbis-1.1.2-2 (not affected?)
• mikmod-3.1.6-38.1 (not affected?)
• numactl-0.9.8-2 (not affected?)
• vorbis-tools-1.1.1-3 (not affected?)

Confirmed

• mesa-6.5.1-7.2 (confirmed)
• procps-3.2.7-8.1 (confirmed)

Original build logs (affected packages):

• Original Build Log: mesa-6.5.1-7.2.build.log.bz2

• Original Build Log: procps-3.2.7-8.1.el5.build.log.bz2

We are Currently working on patches to rebuild the affected packages without the -ffast-math for i586 arch only.

We are currently unaware of other issues, and will add them here when they are found.