Re: [gentoo-user] Hardware upgrade and Gentoo

[Alex Schuster]

Daniel da Veiga writes:

> I just got a new box for use at work, its an Intel Core Duo 1.8, 1GB
> RAM, with an Intel graphic card, its a IBM Lenovo machine. My old one
> is an Itautec Athlon XP 1.1GHz with 512MB RAM and an Nvidia AGP
> graphic card.
>
> My make.conf (intersting part):
> CFLAGS="-mno-tls-direct-seg-refs -O2 -pipe -fomit-frame-pointer
> -march=athlon-xp"
> CHOST="i686-pc-linux-gnu"
> CXXFLAGS="${CFLAGS}"
> MAKEOPTS="-j2"
>
> What I want to know is, will my software, compiled with the above
> settings, run in the new processor?

I think this will not work well, because your current system has 
Athlon-specific CPU instructions which the Intel machine dows not know 
of. You probably get "illegal instruction" errors with many binaries. I 
even had this when I replaced my athlon-something with a just slightly 
less powerful Sempron CPU. 

> Anyway, should I start from scratch or there's an easy way to migrate
> all this stuff?

This should help, if you have exchanged the hardware and experience 
problems:
http://www.gentoo.org/proj/en/portage/doc/manually-fixing-portage.xml

However, see this thread, where it did not seem to work:
http://archives.gentoo.org/gentoo-user/msg_114280.xml

Another method, which I would use, would be to change your CFLAGS to what 
you would like for the new processor, but use mtune= instead of march=. 
This will also optimize for the cpu, but the code will run on any x86 
CPU. emerge world --emptytree to re-compile everything, then switch your 
hardware. This will give you flexibility, at the cost of lesser 
optimization. Depends on how you use your system, most applications will 
not show a noticeable speed ddifference I guess. 
You could also change to march= later, when the system ist up, and 
re-compile everything again to get full optimization.

	Alex
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