Re: [gentoo-amd64] New install - basic question

[Josh Sled <jsled@asynchronous.org>]

Paul Stear <gentoo@appjaws.plus.com> writes:
> I am currently using amd64 2 core processor but now have the chance to use 
> an intel quad 64 processor.
> This might be a silly question but is it best to do a compltly new
> install?
[…]
> Which chost and cflags should I use?

I just did this transition a couple of weeks ago … Athlon 64 X2 to
i7-950.  You don't need to do a full reinstall.

I found http://forums.gentoo.org/viewtopic-t-715522-start-150.html?sid=da3871db3f6144b9f9c4c9dabe34c6d4
interesting reading leading up to the change, especially ezakimak2's
post of 2010-04-12 15:00.

I did the same procedure as he outlines:

- edit /etc/make.conf to change CFLAGS from -march=k8 to -march=generic
- `emerge system`
- rebuilt kernel for generic i686, new mobo
- shut down, swap hardware, start up
- edit /etc/make.conf to change CFLAGS to -march=native
- `emerge system`

The biggest problem I had was not building a kernel that included all
the drivers appropriate to my new motherboard, leading to kernel panic
immediately on startup and many hours spent that day with System Rescue
CD. :( Unfortunately, SystemRescueCD seemed to identify my boot drive
and raid/lvm setup wrong, which was very distressing and misleading for
most of that time.  Once I figured that out and re-mounted everything
correctly, I was able to chroot into my own system as per
http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=6#doc_chap1
and build and install an appropriate kernel.


I did change some USE flags and rebuilt media packages, but I haven't
needed to rebuild anything else, yet.  X, Gnome, emacs, Chrome, &c. all
ran perfectly fine after things were up and running; I wasn't running
any particularly crazy CFLAGS before.

http://en.gentoo-wiki.com/wiki/Safe_Cflags is always a good reference
for CFLAGS, though as they point out, these days it's just
"-march=native" and let GCC figure it out.

CHOST should be unchanged from your current setting:
CHOST="x86_64-pc-linux-gnu".  If this is not your current setting, then
you are not running 64-bit, and you might want to take the opportunity
to do a complete reinstall, yes.

-- 
...jsled
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