Mailing List Archive

Il 05/02/2011 16:45, Paul Stear ha scritto:
> If so which stage do I download from the following list:-
amd64 or if you want x86

> Which chost and cflags should I use?
CHOST="x86_64-pc-linux-gnu" for amd64
CFLAGS="-march=native -O2"
CXXFLAGS="${CFLAGS}"
LDFLAGS="${LDFLAGS} -Wl,--hash-style=gnu"

Enjoy!

--
Agostino Sarubbo ( ago )
Mail: ago@autistici.org
Gpg: 0x7CD2DC5D
Arch Tester for Gentoo Linux amd64 http://is.gd/hcQem
Admin for HacklabCS c/o HPCC at Unical

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
http://asynchronous.org/ - a=jsled; b=asynchronous.org; echo ${a}@${b}

Am 05.02.2011 16:45, schrieb Paul Stear:
> Sorry original sent to the wrong list.
>
> Hi,
> 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?
> If so which stage do I download from the following list:-
>
> alpha: iso stages
> amd64: iso stages
> arm: stages
> hppa: stages
> ia64: iso stages
> ppc/ppc64: iso stages
> s390/s390x: stages
> sh: stages
> sparc: iso stages
> x86: iso stages
>
> Which chost and cflags should I use?
>
> Thanks for any help
> paul

It's amd64, as well. Unfortunately, depending on your CFLAGS you might
still have incompatible code on your current system. You can still try
it but you will likely encounter random process crashes because of
invalid opcodes.

You can avoid a complete reinstall by changing your CFLAGS to something
generic like '-march=i686' and remove anything else not supported by
both processor families.
Then make a `emerge --emptytree world` to recompile all packages.

Don't forget to adjust your kernel as well.

For your specific CFLAGS, look here:
http://en.gentoo-wiki.com/wiki/Safe_Cflags/Intel

Hope this helps,
Florian Philipp

On Sat, 5 Feb 2011 15:45:08 +0000
Paul Stear <gentoo@appjaws.plus.com> wrote:

> 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?

As long as you are using Gentoo 64-bit there is no need for a new
install. The only difference is the number of cores, and perhaps
some new FPU options.

> Which chost and cflags should I use?

CHOST is the same. No change.

CFLAGS may need to be altered. Some Intel quads have SSE 4.1 while others
have SSE 3. You need to check the exact processor version to find out
which is present.

Also you can set MAKEOPTS="-j5" for the quad processor.

If you are compiling your own kernel, you may want to change the
NR_CPUS configure option to 4, and if the new cpu has hyperthreading
as well, then also select SCHED_SMT.

I assume that for the previous Core2 duo you already have the multi-core
scheduler support, SCHED_MC, selected.

Beyond these small changes, nothing new is required. Just pop the
new quad in and go.

Frank Peters

Paul Stear posted on Sat, 05 Feb 2011 15:45:08 +0000 as excerpted:

> 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? If so which stage do I download from the following list:-
>
> alpha: iso stages
> amd64: iso stages
> arm: stages
> hppa: stages
> ia64: iso stages
> ppc/ppc64: iso stages
> s390/s390x: stages
> sh: stages
> sparc: iso stages
> x86: iso stages
>
> Which chost and cflags should I use?

Intel em64t (as opposed to the Itanics/Itaniums) is amd64 by another name.
So use the amd64 stages if you want 64-bit, or the x86 stages if you want
legacy 32-bit. (FWIW, ia64, Intel Arch 64, would be for the Itaniums.
Sometimes people get that mixed up, but unless you know you have that
hardware, it's pretty safe to assume it's amd64/em64t/x86_64, NOT ia64.)

Assuming amd64, whether you /have/ to start from fresh stages or can use
your existing install, depends on how similar the hardware extensions are,
and whether you used -march or -mtune on your previous install. If you
used -mtune, the old install should work as it will have used only
instruction ordering for your target hardware, with generic instructions.
If you used -march, it will have used targeted instructions as well, and
may or may not work. You can try it if you like as going older to newer
it's likely to work, but really, starting with a new CPU is a good excuse
to start fresh, eliminating any possible cruft left over from the old
system, so I'd recommend starting from new stages even if the old ones
would work, unless you're lazy and simply want to avoid that extra
compiling.

If you want to target the new hardware and are using a new enough gcc (I
think the stage supplied one is new enough, now), you can simply use
-march=native to take advantage of its instructions. If you'd prefer to
have the compiled packages be installable on either machine (say if you
run FEATURES=buildpkg to get the binpkgs to do so), but tuned for the new
one, use -mtune=native on the new one instead, possibly with -march set
for the common subset of both instruction sets, tho you'd of course have
to set that subset specifically, which means researching what it is.

CHOST will normally be the same, x86_64-pc-linux-gnu , unless you're doing
something strange or using legacy 32-bit x86 instead of amd64.

--
Duncan - List replies preferred. No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman

Thank you to Duncan, Frank, Florian, Josh and Agostino for your replies.
I am pleased that it appears that I do not need to reinstall from scratch.
I am just starting emerge system so I will see what has happed in the morning.
regards
Paul
--
This message has been sent using kmail on gentoo.