On 4/2/2011, at 5:58am, Florian Philipp wrote:
>> ...
>> The warning is actually there to stop users doing stupid things like blindly
>> trying to convert 32 bit systems to 64 bit. This is how that goes down:
>>
>> 1. Change CHOST
>> 2. emerge -e world
>> 3. ???
>> 4. Fail!
>
> Is the same true for more compatible arches like i486 -> i686? I have a
> system where I used the wrong stage-3 and now I'm stuck with an i486
> CHOST on an Atom netbook where I could use every bit of performance.
I'm in the process of this at the moment.
I have a Cobalt Qube III, which has a K6-2 CPU, and which will never
accommodate any other processor.
The closest Gentoo stage was i486, and on such a slow old system it would be
nice to squeeze out any extra performance I can.
From the i486 stage I used:
# cat /etc/make.conf.catalyst
# These settings were set by the catalyst build script that automatically
# built this stage.
CFLAGS="-O2 -march=i486 -pipe"
CXXFLAGS="${CFLAGS}"
# WARNING: Changing your CHOST ...
# Please consult http://www.gentoo.org/doc/en/change-chost.xml before changing.
CHOST="i486-pc-linux-gnu"
Following the instructions I changed the CHOST (to i586) and did the `emerge -1
binutils gcc glibc` part.
That went fine, so I changed CFLAGS="-march=native -O2 -pipe
-fomit-frame-pointer", and followed the next steps up to 2.12 - `emerge -e
world`.
This failed about 3 packages in and really messed things up - I quickly
couldn't emerge anything else and running executables failed with a segfault or
something.
I had to pull the drive back out of the Qube and copy most of the i486 stage
back over the fouled-up installation.
This time around, I changed the CHOST again to i586 and ran `emerge -1 binutils
gcc glibc`, then `lafilefixer --justfixit && revdep-rebuild` (didn't need to do
anything, it said) then the `emerge -e world` part - but this time still with
the original i486 CFLAGS (as the catalyst above). This is currently at "104 of
145" packages through the emerge process, so seems ok.
Hopefully when that's done I'll be able to change CFLAGS to "-march=native" and
re-emerge the whole lot again. I'm now a bit nervous of that (I'm wondering if
`-mcpu` or `-mtune` would be more suitable as a first step), so I'll take a
disk image using dd (again) so that I have a restore point, should I need it.
Stroller.
