Fedora kernel packaging changes

We recently made a change in Fedora kernel packaging, to drop the regular 686 kernels. As of Fedora 11, the only 32-bit kernels built are ’586′ and ’686-PAE’ (and their -debug variants).

In F11, at install-time, Anaconda will install the PAE kernel if the CPU is capable of using it, and otherwise, will fall back to the 586 kernel. (Users upgrading with yum will see a 686->586 transition unless they are already using the -PAE flavour)

Both kernels actually have instruction scheduling optimised for 686 (Using gcc’s -mtune=generic, which optimises for the popular CPUs of the time).

The actual differences between the two builds:

586:

  • Uses only up to the i586 ISA

  • Supports up to 4GB of RAM.
  • Will use segment limits to approximate NX.

686-PAE:

  • Uses the 686 ISA including CMOV.

  • Uses 3-level page-tables allowing >4GB RAM.
  • Where possible, uses hardware NX instead of segment limits. (faster)
  • Has Xen virtualisation enabled.

Processors that will need to use the 586 kernel include..

  • all AMD CPUs prior to the Athlon

  • Intel Pentiums prior to the Pentium Pro
  • Some subset of Intel Pentium M’s (These are the only ‘modern’ CPUs)
  • All Cyrix and Transmeta
  • All VIA prior to Esther

3 thoughts on “Fedora kernel packaging changes

  1. AdamHough

    https://fedoraproject.org/wiki/Features/ArchitectureSupport
    “or Fedora 11, we’d like to revisit what architectures Fedora supports, and change some of our defaults so that we work better on those architectures.

    The main user-visible changes would be:

    * 32-bit x86 would be built for i586 by default.
    * The x86_64 kernel would be installed on compatible hardware, even when installing a 32-bit OS
    * The PAE kernel would be installed on other 32-bit hardware, where it is supported

    The 32-bit LiveCD would remain using a 32-bit kernel, in all likelyhood.

    Have you seen this link yet. There is also a discussion on the fedora-devel with the title “Features/ArchitectureSupport – changing what we build for” discussing this topic as well.

    I say this because you did not seem to mention anything about the x86_64 kernel for 32-bit installs, and was wondering if you had heard or seen anything about this?

    1. davej Post author

      yeah, that’s happening too, I probably should have mentioned it at least in passing, though maybe it deserves a separate post to keep this one simple.

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