[gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Denis]

Are these any options in the kernel and in the gcc to optimize for
Intel's Core 2 Duo chips?  When I set up my gentoo box for the Pentium
Processor Extreme Edition (dual core prescott), I just used
-march=prescott in make.conf

Which -march flag would be the most relevant gcc optimization for
Intel Core 2 Duo?

And is there explicit support in the latest gentoo kernel for Core 2
Duo, or does it go under Pentium 4 family?

Thanks
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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Ryan Sims]

On 5/24/07, Denis <denis.che@gmail.com> wrote:
> Are these any options in the kernel and in the gcc to optimize for
> Intel's Core 2 Duo chips?  When I set up my gentoo box for the Pentium
> Processor Extreme Edition (dual core prescott), I just used
> -march=prescott in make.conf
>
> Which -march flag would be the most relevant gcc optimization for
> Intel Core 2 Duo?
>
> And is there explicit support in the latest gentoo kernel for Core 2
> Duo, or does it go under Pentium 4 family?
>

Google is your friend:
http://www.google.com/search?q=core+2+duo+cflags
http://gentoo-wiki.com/Safe_Cflags#Intel_Core_2_Duo.2FQuad_.2F_Xeon_51xx.2F53xx



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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Mark Shields]

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On 5/24/07, Denis <denis.che@gmail.com> wrote:
>
> Are these any options in the kernel and in the gcc to optimize for
> Intel's Core 2 Duo chips?  When I set up my gentoo box for the Pentium
> Processor Extreme Edition (dual core prescott), I just used
> -march=prescott in make.conf
>
> Which -march flag would be the most relevant gcc optimization for
> Intel Core 2 Duo?
>
> And is there explicit support in the latest gentoo kernel for Core 2
> Duo, or does it go under Pentium 4 family?
>
> Thanks
> --
> gentoo-user@gentoo.org mailing list
>
>
A gentoo forum thread[1] states to use -march=nocona for Core 2 Duo, and
-march=prescott for Core  Solo/Duo.

[1] http://forums.gentoo.org/viewtopic-p-3602555.html


-- 
- Mark Shields

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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Denis]

After reading some docs, the impression I get is that the 'nocona'
flag is for building a 64-bit system...  For a 32-bit system, it seems
like 'prescott' would be the choice, wouldn't it?

This from the GCC website about 4.2.0 release changes:

IA-32/x86-64

    * -mtune=generic can now be used to generate code running well on
common x86 chips. This includes AMD Athlon, AMD Opteron, Intel
Pentium-M, Intel Pentium 4 and Intel Core 2.
    * -mtune=native and -march=native will produce code optimized for
the host architecture as detected using the cpuid instruction.
    * Added a new command line option -fstackrealign and and
__attribute__ ((force_align_arg_pointer)) to realign the stack at
runtime. This allows functions compiled with a vector-aligned stack to
be invoked from legacy objects that keep only word-alignment.

We don't have gcc-4.2.0 in our portage available for installation yet,
do we?  Anyone know when?
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[gentoo-user] Re: which -march flag to pick for Intel Core 2 Duo in make.conf?

[Alexander Skwar]

Denis <denis.che@gmail.com> wrote:

> Are these any options in the kernel and in the gcc to optimize for
> Intel's Core 2 Duo chips?

In the kernel: Yes. At least in 2.6.21. 

> And is there explicit support in the latest gentoo kernel for Core 2
> Duo, or does it go under Pentium 4 family?

I'd say, it goes under Core2 -> MCORE2.

Alexander Skwar

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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Neil Bothwick]

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On Thu, 24 May 2007 11:13:30 -0400, Denis wrote:

> After reading some docs, the impression I get is that the 'nocona'
> flag is for building a 64-bit system...  For a 32-bit system, it seems
> like 'prescott' would be the choice, wouldn't it?

Yes.


> We don't have gcc-4.2.0 in our portage available for installation yet,
> do we?  Anyone know when?

When the devs consider it suitable for at least the testing branch or
when you do "echo =sys-devel/gcc-4.2*" >>/etc/portage/package.mask,
whichever comes sooner.

Bear in mind that GCC is almost certainly masked for good reason. It's
not like you're using a binary distro and only need a compiler for a few
packages. Feel free to try it in the knowledge that if it breaks your
system, you get to keep the pieces.


-- 
Neil Bothwick

Sects, sects, sects, is that all you monks think about?

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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Graham Murray]

Neil Bothwick <neil@digimed.co.uk> writes:

> When the devs consider it suitable for at least the testing branch or
> when you do "echo =sys-devel/gcc-4.2*" >>/etc/portage/package.mask,
> whichever comes sooner.

Even that will not work (yet) as gcc-4.2 is not actually masked it is
not keyworded.
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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Denis]

On 5/24/07, Neil Bothwick <neil@digimed.co.uk> wrote:
> Bear in mind that GCC is almost certainly masked for good reason. It's
> not like you're using a binary distro and only need a compiler for a few
> packages. Feel free to try it in the knowledge that if it breaks your
> system, you get to keep the pieces.

Ain't it the truth!  No, I wasn't asking with the anxiety to hurry
things up - I was asking more about an estimated release time, whether
it will be a month, 2 months, 3 months, etc.

I'm not really looking to "experiment" with the cutting-edge releases
right now.  My aim is to build a fast, stable system for my
computations, which ultimately brought me to another major decision:
32-bit or 64-bit...  I run simulations which I write in C and
numerical computations which I run in Mathematica (which has just
released the 64-bit version).  Would a 64-bit system significantly
benefit these applications?
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Re: [gentoo-user] which -march flag to pick for Intel Core 2 Duo in make.conf?

[Randy Barlow]

On Thu, May 24, 2007 12:38 pm, Denis wrote:
> My aim is to build a fast, stable system for my
> computations, which ultimately brought me to another major decision:
> 32-bit or 64-bit...  I run simulations which I write in C and
> numerical computations which I run in Mathematica (which has just
> released the 64-bit version).  Would a 64-bit system significantly
> benefit these applications?

If you are using a lot of memory in your computations, then the 64-bit
environment will be much friendlier to you :)  Also, if I understand
correctly, you will get higher precision on floating point calculations
(someone correct me if I am wrong here!)  I also believe that the 64 bit
processors are able to perform more instructions per second on average
when executing 64 bit code vs. 32 bit code if I am not mistaken...

-- 
Randy Barlow
http://www.electronsweatshop.com
"Oh me of little faith..."
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