Re: [gentoo-user] new install for a new mainboard?

[Rich Freeman]

On Thu, Dec 10, 2020 at 4:18 PM n952162 <n952162@×××.de> wrote:
>
> On 12/10/20 7:18 PM, Rich Freeman wrote:
> > On Thu, Dec 10, 2020 at 10:23 AM n952162 <n952162@×××.de> wrote:
> >> I need a new mainboard.  What will happen if I boot my existing system
> >> on it?
> > Is the CPU going to be the same?  The responses already cover the
> > mainboard itself well.  If the CPU could change then you need to check
> > your -march in CFLAGS for compatibility (if you set it) and
> > potentially rebuild anything you don't want to break.
> >
>
> How would I do that?  Would I have to set up a cross-compiler toolchain?

Nope, just remove -march from your CFLAGS (maybe change it to -mtune)
and emerge -e @world (or @system if you don't care if non-system
packages are broken on the new system).

It is only necessary if you're switching CPUs.  If you're using -march
then your binaries are not guaranteed to run on ANY CPU other than the
one specified, and you'd be surprised how non-backwards-compatible
CPUs can be.  With gcc the -march option tells the compiler that it
can use any instruction it can to optimize things, including ones that
are very uncommon on other CPU models.  -mtune makes optimizations but
the code will run on any CPU for that architecture.

You can try to find a least-common-denominator CPU but it usually
isn't worth the hassle.

-- 
Rich