2009/4/5 drago01 drago01@gmail.com

On Sun, Apr 5, 2009 at 9:15 PM, Antonio Olivares olivares14031@yahoo.com wrote:

...

Dear fellow testers,

I am sorry to ask, but I read about the changes on i686 moving to i586

and the i386 packages to i586. I had known prior to this that

...

i686 ---> Pentium computer PIII, PIV, Intel based CPU i586 ---> AMD athlon, other AMD capable computer x86_64 ---> AMD 64 capable CPU or similar processor

The default 32-bit x86 target in koji would be changed from i386 to i586 http://fedoraproject.org/wiki/Features/ArchitectureSupport

I assume this is only temporary as after this release it will go back to

i686 right?

...

The other distributions I am familiar with that used i586 packages are

OpenSUSE and Mandriva namely. This only makes me confused as the i586 packages are optimized for AMD processors and the i686 packages for Intel based CPU's like Pentium III/IV.

...

I am only a bit confused with this and if someone can help me undestand

better I would appreciate it very much :)

ix68 has nothing to do with the cpu vendor (AMD, INTEL, VIA) it just means the minimum required instruction set that is needed for the software to run. i586 means "Pentium or older"

i686 is pentium pro and later (or compatible), i586-only is refered to all other pentium (or compatible), and i386-only is all intel compatible starting with i386 and lower than pentium. see also http://en.wikipedia.org/wiki/I686

however it may be interesting to hear what fedora package builders have to say on this matter.

-- fedora-test-list mailing list fedora-test-list@redhat.com To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-test-list

On Sun, 2009-04-05 at 23:01 +0100, psmith wrote:

i completely understand the reasoning to move i365 up to i586, but why on earth restrict i686 capable processors to the i586 instruction sets?

Again: the only difference between i586 and i686 is the CMOV family of instructions, which are generally *slower* than the i586 version.

You can read Linus' detailed explanation here: http://ondioline.org/mail/cmov-a-bad-idea-on-out-of-order-cpus

Building for i686 gives *no* real performance benefit[1], but breaks support for i586 machines - Via C7-based netbooks, AMD Geode (e.g. the OLPC XO-1), and so on.

-w

[1] except on in-order CPUs like Atom and the original Pentium

Jan Pazdziora wrote:

On Sun, Apr 05, 2009 at 08:05:41PM -0400, Will Woods wrote:

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Building for i686 gives *no* real performance benefit[1], but breaks support for i586 machines - Via C7-based netbooks, AMD Geode (e.g. the OLPC XO-1), and so on.

-w

[1] except on in-order CPUs like Atom and the original Pentium

Does this mean that for Atom-based machines we are taking the risk of introducing some slowdown?

I compiled scimark using march=i686/i586 (both with tune=i686) and on an atom notebook the scores were 166+/-1 for both versions. Any change in performance is in the noise region. There are code changes but according to objdump the 586 compiled version did not use any CMOVs.

Will Woods wrote:

On Sun, 2009-04-05 at 23:01 +0100, psmith wrote:

...

i completely understand the reasoning to move i365 up to i586, but why on earth restrict i686 capable processors to the i586 instruction sets?

Again: the only difference between i586 and i686 is the CMOV family of instructions, which are generally *slower* than the i586 version.

You can read Linus' detailed explanation here: http://ondioline.org/mail/cmov-a-bad-idea-on-out-of-order-cpus

Building for i686 gives *no* real performance benefit[1], but breaks support for i586 machines - Via C7-based netbooks, AMD Geode (e.g. the OLPC XO-1), and so on.

-w

[1] except on in-order CPUs like Atom and the original Pentium

well i understand why fedora stuck with downgrading to i586 now, saving work by only having to compile 1 kernel version for the x86 arch (plus to keep the olpc folks happy i suppose) and while linus is undoubtably a clever guy i think intel know their arch better than anyone, and if cmov was a performance hit it would be removed ;) looks like i'll need to compile my own i686 for my aspire one as the i586 kernel in F11 beta is showing a noticeable performance hit over F10 i686 :(

phil

On Mon, 06 Apr 2009 11:30:47 +0100, psmith wrote:

was a performance hit it would be removed ;) looks like i'll need to compile my own i686 for my aspire one as the i586 kernel in F11 beta is showing a noticeable performance hit over F10 i686 :(

First try to rebuild the F11 kernel with debugging options disabled.

On Mon, Apr 06, 2009 at 10:57:48AM -0400, Bill Nottingham wrote:

Actually, in some testing I did, the fasted was '-march=i686 -mtune=generic' (which was ~1% faster than '-march=i586 -mtune=generic'), tested across Core2Duo, Athlon64, and Atom.

Twiddling the instruction scheduling (-mtune) invariably made things worse, across the board.

Even with -mtune=atom on Atom CPUs?

Jakub

I'm planning to add the below to the F11 beta release notes under "What's New" in a few days, but please let me know if there are any objections, corrections, clarifications, etc.

-B.

===Package rebuild===

All .i386 and .i486 packages have been rebuilt as .i586 (Pentium class). These designations represent the ''minimum'' supported architecture version; Fedora 11 is ''optimized'' for Pentium 4-compatible and later processors. Fedora has never officially supported pre-Pentium architectures, and dropping any remaining backwards compatibility with these chips further improves performance and allows for code simplification (for example in glibc).

===.i386/.i686 kernel changes===

As part of the package rebuild (described above), the kernel.i386 RPM is no longer produced. For different reasons, the kernel.i686 RPM is also no longer built. The following kernel choices ''are'' available in Fedora 11:

* kernel.i586, for those requiring compatibility with a Pentium-class architecture or who do not have a PAE and NX capable processor. * kernel-PAE.i686, which requires a PAE and NX capable processor with Pentium PRO-class or later architecture.

These designations represent the ''minimum'' supported architecture version; Fedora 11 is ''optimized'' for Pentium 4-compatible and later processors.

After analyzing the differences between the i585 and i686 architectures, dropping the non-PAE i686 kernel is not expected to have a negative performance impact for those required to drop to the kernel.i586 package. The kernel-PAE.i686 RPM supports security features like ExecShield, and can address up to 64GB of RAM (up from 4GB for the standard kernel).

Anaconda (the recommended install method) will automatically choose the best kernel.

If you are using the "yum upgrade" method (not recommended), you may receive the kernel.i586 package even if your processor would support the kernel-PAE.i686 package. To determine this, run the command:

:grep 'flags.* pae' /proc/cpuinfo | grep -wq nx && echo 'kernel-PAE'

If you see "kernel-PAE" in the output, then your CPU is capable of using this package, and you can manually "yum install kernel-PAE".

On Tuesday, April 14 2009, Chris Adams said:

I know it is a little late to ask, but:

Once upon a time, Christopher Beland beland@alum.mit.edu said:

...

• kernel.i586, for those requiring compatibility with a Pentium-class

architecture or who do not have a PAE and NX capable processor.

• kernel-PAE.i686, which requires a PAE and NX capable processor with

Pentium PRO-class or later architecture.

Why isn't the i686 kernel just "kernel" as well? Is there going to be some other kernel.i686 package later?

Because kernel-PAE requires that your processor support PAE and not all i686 capable processors do

Jeremy

On Wed, 2009-04-15 at 00:10 -0400, Ignacio Vazquez-Abrams wrote:

I don't think there's been a kernel.i386 for a long time. Perhaps you were thinking of kernel-headers.i386.

Ah, you're right - I wasn't reading carefully. The notes should then read as follows:

===Package rebuild===

All .i386 and .i486 packages have been rebuilt as .i586 (Pentium class). These designations represent the ''minimum'' supported architecture version; Fedora 11 is ''optimized'' for Pentium 4-compatible and later processors. Fedora has never officially supported pre-Pentium architectures, and dropping any remaining backwards compatibility with these chips further improves performance and allows for code simplification (for example in glibc).

===.i686 kernel changes===

The kernel.i686 RPM is no longer produced. The following kernels are available instead:

* kernel.i586, for those requiring compatibility with a Pentium-class architecture or who do not have a PAE and NX capable processor. * kernel-PAE.i686, which requires a PAE and NX capable processor with Pentium PRO-class or later architecture.

After analyzing the differences between the i585 and i686 architectures, dropping the non-PAE i686 kernel is not expected to have a negative performance impact for those required to use the kernel.i586 package. The kernel-PAE.i686 RPM has additional capabilities, such as support for ExecShield security and the ability to address up to 64GB of RAM (the standard kernel can address only 4GB). Note that the architecture designations in RPM names represent the ''minimum'' supported architecture version; Fedora 11 is ''optimized'' for Pentium 4-compatible and later processors.

Anaconda (the recommended install method) will automatically choose the best kernel for your hardware.

If you are using the "yum upgrade" method (not recommended), you may receive the kernel.i586 package even if your processor would support the kernel-PAE.i686 package. To determine this, run the command:

:grep 'flags.* pae' /proc/cpuinfo | grep -wq nx && echo 'kernel-PAE'

If you see "kernel-PAE" in the output, then your CPU is capable of using this package, and you can manually "yum install kernel-PAE".

On Thu, 2009-05-28 at 03:09 -0400, Christopher Beland wrote:

Oops, this never made it into the release notes, so this is the next best place I could find:

https://fedoraproject.org/wiki/Common_F11_bugs#Can.27t_find_.i686_kernel

Please don't add issues which are not bugs to the Common Bugs page. As Susan Lauber mentioned a few posts back, there are ways to add issues to the live version of the Release Notes after release. Please do this, Susan can help you if necessary. Once that's done, please remove this from the Common Bugs page.

Additionally, the bit about a potential gotcha on yum upgrade should go on the dedicated page for upgrading via yum:

https://fedoraproject.org/wiki/Upgrading_Fedora_using_yum#10-11

I just want to make sure the release notes are clear on what is changing...

The Fedora 6 thru 10 release notes say "Fedora __ requires an Intel Pentium or better processor, and is optimized for Pentium 4 and later processors." The same policy goes back with different words to at least Fedora Core 2. ("Pentium" being i586, and I gather from Wikipedia that Pentium 4 = Intel NetBurst = i786?)

So am I correct in assuming that all the i386 packages, including the i386 kernel, were backwards-compatible with i386 and i486 CPUs, even though officially these CPUs were not supported in Fedora 2 thru 10?

If so, wouldn't a small number of users who inexplicably still have i386 and i486 chips find that this is the first Fedora release that does not work for them, or is it simply impossible that there is anyone still running it on these architectures? (I don't seen anything below i586 in the smolt "active hosts" database.)

The benefits listed on the feature page are:

...

By optimizing better for the architectures which we support, we give better performance to our users.

By using the PAE kernel where appropriate, we allow features like ExecShield to be used.

By changing the minimum kernel for glibc, we allow the removal of various hacks, tests, and workarounds in the glibc code. <<

Would a polished version of this be appropriate to add to the "What's New" section of the release notes?

As for the i586/i686 business, is the following an accurate understanding? * Users needing compatibility with the i586 instruction set may use the kernel.i586 package. * Users with PAE and NX capable CPUs may use the kernel-PAE.i686 package. * i686 users without PAE and NX capabilities can also use the kernel.i586 package, which will not impact performance except for in-order CPUs like Intel's Atom. * Both the kernel.i586 and kernel-PAE.i686 packages are optimized for Pentium 4 compatible chips; the architecture designation indicates the earliest chips with which the build is compatible.

It also sounds like this might be good advice?:

...

* Anaconda will automatically choose the best kernel for the system. * If using the "yum upgrade" method (not recommended), you may need to install the kernel-PAE.i686 package manually if you have a CPU with PAE and NX capabilities. To determine this, run the command: grep 'flags.* pae' /proc/cpuinfo | grep -wq nx && echo 'kernel-PAE' If you see "kernel-PAE" in the output, then your CPU does have these capabilities. <<

-B.

On Sun, 2009-04-05 at 17:12 -0400, Will Woods wrote:

If your CPU supports PAE and NX[2] (or you have >4GB RAM), anaconda will install kernel-PAE.i686 - otherwise the basic kernel.i586 package will be used[3].

...

[1] In-order CPUs (like Intel's Atom) do benefit from CMOV. [2] grep 'flags.* pae' /proc/cpuinfo | grep -wq nx && echo 'kernel-PAE' [3] F10 and earlier systems with kernel.i686 will get kernel.i586 as an upgrade - if your system is PAE capable you might want to install kernel-PAE manually, since using PAE+NX *is* a significant performance benefit.

On Mon, Apr 06, 2009 at 10:04:29 +0200, Kevin Kofler kevin.kofler@chello.at wrote:

Fedora already didn't work on those machines because there was no kernel for them. You needed a third-party kernel to even install Fedora on them. And

Also giben the amount of memory typically on machines of that era, you aren't likely to be able to install Fedora on them because of too little memory.