Why there is no athlon specific kernel in Fedora core 1/2 ?

[Darragh Bailey]

> On Tue, 2004-07-27 at 14:25 +0100, Paul wrote:
> > Certainly from the 2.6 kernel there wasn't an Athlon option - mainly as
> > the kernel now self detects the processor and applies the optimisations
> > itself. You just have to use the i686 version to access this.

Actually I thought what they did was to alter some of the makefiles so that
depending on what target CPU you selected from the config options the makefiles
would set the correct optimization flags for that target, negating the need for
you to pass which CPU from the family you were using in order to get the
correct optimizations. Makes sense really, in that you've already stated it in
the config file what CPU its going to be for.

Would appreciate someone clearing that bit up though, as I can't find a
definitive explaination on this, i.e. as to whether it definitely works backed
up with links to approiate articles explaining how it works. Kernel docs don't
seem to be providing anything about this either, unless I'm stareing at the
wrong files.

Not that I'm dismissing the possiblity, I'm quite interested in the idea, but
since searching with google hasn't turned up anying good on this, and I can't
find anything deffitive on this, I am uncertain as to what exactly the kernel is
doing when it encounters different CPU architectures and how well it can
optimize for the different CPU's

Any further details or a good link on that particular subject would be
appreciated (or even better search terms for google :) )


In any case I was feeling pedantic about being able to specify athlon and have a
separate athlon config so I went about modifying the spec file and generating a
new config file. Besides, I wanted to be able to strip out a lot of the extra
drivers, etc, and add in a few things that are missing.


> There certainly IS an option in 2.6 for Athlon- it is CONFIG_MK7, in the
> kernel config menu it is under "Processor type and features -->
> Processor Family" (with Subarchitecture type set to "PC-compatible").
>
> Note: I've been using the kernel-source rpm to build custom kernels,
> rather than trying to use the kernel SRPM (I also am not yet up to the
> latest FC2 kernel on my laptop), so I can't say what the issue is with
> the original poster, but I suspect he'll need to update the spec file as
> well as the kernel config used in the SRPM.

Yeah, there's a couple of problems with the spec file that you need to sort if
you want to be able to specifiy athlon as a target.

I've attached (normally I'd just still it up in my webspace and post the url
here but the webspace is currently out of action at the moment, so apologies if
people don't appreciate the attachments. I've bzip'ed them to make them as small
as possible.) my own version of the spec file + config file which should work
just fine, its basically just the i686 config file changed for the athlon using
the config menu's and saved. Then run using the "make ARCH=i386
nonint_oldconfig" to make sure it wouldn't have any issues when that is
performed silently. Just remember I haven't used that particular config file, as
I normally edit it further to strip out all the unnessary items not required for
my system and add in some of the extras that I want, such as nfts read support.


steps in general
install SRPM
unpack resulting tarball from /usr/src/redhat/SOURCES to /usr/src/redhat/BUILD
apply all the patches
go to /usr/src/redhat/BUILD/kernel-2.6.6/linux-2.6.6/ (might be slightly
different names)
make oldconfig
make gconfig or make xconfig, etc
    save the config file
make ARCH=i386 nonint_oldconfig (this is where issues with the config file will
cause a crap out, running it twice might solve your problem, but if it doesn't
pass this, you won't be able to create a new rpm using it.)
Once you have a config file that can pass this step then you can add it to the
rest of the sources, I renamed mine to kernel-2.6.6-athlon.config and copied it
to a safe location as well as /usr/src/redhat/SOURCES

modify the the kernel-2.6.6.spec file under /usr/src/redhat/SPECS to add the
entries to be able to use the new config file as well as handle being passed
the target athlon. You could of course just copy your new config file over one
of the existing ones in the SOURCES directory and set the target option so that
it will use that one.

You can simply use my provided config file and spec file and copy them into the
source folder and spec folder respectively after installing the SRPM and issue
the command from /usr/src/redhat/
rpmbuild -bs SPEC/kernel-2.6.spec

which will generate a new SRPM that you can use to build the binaries from. Just
remember that I'm using version 2.6.6-1.435.2.3, so if you go to use the config
file with any other version you will need to use the 
make ARCH=i386 nonint_oldconfig
command to take care of any config changes before you attempt to compile a new
kernel from it.

Areas that I altered, 

# groups of related archs
%define all_x86 i586 i686 athlon

added an %ifarch for athlon as well
added a line for the source Source37: kernel-%{kversion}-athlon.config

Also modified the following line
 make ARCH=`echo $i | cut -d"-" -f3 | cut -d"." -f1 | sed -e s/i.86/i386/ -e
s/s390x/s390/ -e s/ppc64.series/ppc64/ -e s/ppc8260/ppc/ -e s/athlon/i386/`
nonint_oldconfig > /dev/null

Athlon still uses the basic i386 arch folder, its just the CFLAGS passed to the
compiler are optimized differently depending on your config file AFAIK.

I suppose I could have left it alone and just copied over my config file over
the i686 file, but as I stated earlier I was being a little pedantic. Besides
its good to be able to understand what the hell is going on in those spec files.


-- 
Darragh

"Nothing's foolproof to a sufficently talented fool"
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