[gentoo-user] New computer and Gentoo

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* [gentoo-user] New computer and Gentoo
@ 2011-07-21  2:23 CJoeB
  2011-07-21  2:29 ` Adam Carter
  0 siblings, 1 reply; 6+ messages in thread
From: CJoeB @ 2011-07-21  2:23 UTC (permalink / raw
  To: gentoo-user

Hi everyone,

Today, I ordered a new desktop from Dell (offer too good to pass up!). 
The system is a Dell XPS 8300 with an Intel Core i7 processor.  I was
reading the Gentoo wiki about safe CFLAGS and it said that march=native
is recommended if I use gcc >= 4.2.3.

I looked at processor specific CFLAGS and if I am understanding this
correctly, for an Intel i7, I would use march=prescott for a 32 bit OS. 
It also mentions march=core2 if using gcc > 4.3 for a 64-bit OS. 
However, it has amd64 in brackets.  So would this be for an amd system?

Should I stick with march="native"?

Advice would be appreciated. 

Regards,

Colleen

-- 

Registered Linux User #411143 with the Linux Counter, http://counter.li.org

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [gentoo-user] New computer and Gentoo
  2011-07-21  2:23 [gentoo-user] New computer and Gentoo CJoeB
@ 2011-07-21  2:29 ` Adam Carter
  2011-07-21  5:26   ` Mick
  0 siblings, 1 reply; 6+ messages in thread
From: Adam Carter @ 2011-07-21  2:29 UTC (permalink / raw
  To: gentoo-user

amd64 means any x86 64bit platform, so Intel too.

march=native is good if you're not using distcc, or if you're only
using distcc on core2 boxes. Otherwise be specific.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [gentoo-user] New computer and Gentoo
  2011-07-21  2:29 ` Adam Carter
@ 2011-07-21  5:26   ` Mick
  2011-07-21  5:54     ` Bill Kenworthy
  0 siblings, 1 reply; 6+ messages in thread
From: Mick @ 2011-07-21  5:26 UTC (permalink / raw
  To: gentoo-user

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On Thursday 21 Jul 2011 03:29:17 Adam Carter wrote:
> amd64 means any x86 64bit platform, so Intel too.
> 
> march=native is good if you're not using distcc, or if you're only
> using distcc on core2 boxes. Otherwise be specific.

I recommend using the "64 bit profile (amd64) for >= GCC 4.3" which shows -
march=core2.  This is what I use here with multilib and had no problems.
-- 
Regards,
Mick

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^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [gentoo-user] New computer and Gentoo
  2011-07-21  5:26   ` Mick
@ 2011-07-21  5:54     ` Bill Kenworthy
  2011-07-21 22:35       ` [gentoo-user] " walt
  0 siblings, 1 reply; 6+ messages in thread
From: Bill Kenworthy @ 2011-07-21  5:54 UTC (permalink / raw
  To: gentoo-user

On Thu, 2011-07-21 at 06:26 +0100, Mick wrote:
> On Thursday 21 Jul 2011 03:29:17 Adam Carter wrote:
> > amd64 means any x86 64bit platform, so Intel too.
> > 
> > march=native is good if you're not using distcc, or if you're only
> > using distcc on core2 boxes. Otherwise be specific.
> 
> I recommend using the "64 bit profile (amd64) for >= GCC 4.3" which shows -
> march=core2.  This is what I use here with multilib and had no problems.

Ive just stumbled on something weird with march=native:

At some point I had march=prescott on a core2 E4600 running 32bit -
worked well.  Changed to march=native and did some upgrades with a few
odd things like asterisk segfaulting in a glibc library afterwards, and
some things not building.  Then to add confusion, I changed to an
pentium Duo E6600 (flies!) and added another stick of ram.  More odd
things happening such as reiserfs oopsing on shutdown.

Last night the penny dropped and I looked the new processor up and
changed to march=core2 and have mostly corrected (recompiled) the
damage.

So not sure about march=native now as it is only what was built with
native thats been problematic.  With 20-20 hindsight it was perhaps
predictable ...

BillK

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [gentoo-user] Re: New computer and Gentoo
  2011-07-21  5:54     ` Bill Kenworthy
@ 2011-07-21 22:35       ` walt
  2011-07-22  6:45         ` Florian Philipp
  0 siblings, 1 reply; 6+ messages in thread
From: walt @ 2011-07-21 22:35 UTC (permalink / raw
  To: gentoo-user

On 07/20/2011 10:54 PM, Bill Kenworthy wrote:

> So not sure about march=native now as it is only what was built with
> native thats been problematic.

Makes me wonder if gcc and glibc need to be recompiled with arch=native
before rebuilding the rest of the system?





^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [gentoo-user] Re: New computer and Gentoo
  2011-07-21 22:35       ` [gentoo-user] " walt
@ 2011-07-22  6:45         ` Florian Philipp
  0 siblings, 0 replies; 6+ messages in thread
From: Florian Philipp @ 2011-07-22  6:45 UTC (permalink / raw
  To: gentoo-user

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Am 22.07.2011 00:35, schrieb walt:
> On 07/20/2011 10:54 PM, Bill Kenworthy wrote:
> 
>> So not sure about march=native now as it is only what was built with
>> native thats been problematic.
> 
> Makes me wonder if gcc and glibc need to be recompiled with arch=native
> before rebuilding the rest of the system?
> 
> 
> 

No. See my posts in the other part of this thread where threading was
once broken by a stupid mobile phone MUA.

Every "native" setting is just resolved by gcc at compile time to some
concrete setting like "core2". There is nothing magical about it and you
also don't need to recompile glibc or gcc any more than you need after
switching your march settings between two other settings.

No one had any breakage during the time when -march=core2 was introduced
and all Core2 owners switched from -march=nocona to -march=core2. There
should be no more breakage when switching to "native".

Correlation does not imply causation.

Regards,
Florian Philipp

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^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2011-07-22  7:03 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-07-21  2:23 [gentoo-user] New computer and Gentoo CJoeB
2011-07-21  2:29 ` Adam Carter
2011-07-21  5:26   ` Mick
2011-07-21  5:54     ` Bill Kenworthy
2011-07-21 22:35       ` [gentoo-user] " walt
2011-07-22  6:45         ` Florian Philipp

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