Re: gcc compiler cputype, prescott or nocona confusion

On 1/31/07, Jorn Argelo <jorn@xxxxxxxxxxxxx> wrote:


On Wed, 31 Jan 2007 23:40:38 +1100, Scott Killen <salkillen@xxxxxxxxxxxxxxxx> wrote:
> Hi,
>
> When recompiling the world or kernel in FreeBSD i386 Rel 6.1 with,
>
> "# make buildworld"
> or
> "# make buildkernel KERNCONF=MYSMPCONF"
>
> (or building anything anything else for that matter), even though I have
> "CPUTYPE?=nocona" set in my "/etc/make.conf" file the compiler seems to
> head
> back to a default of "-march=prescott" when compiling many of the
> functions
> on a Dual Xeon 3.6g (nocona) machine!
>
> This doesn't happen when compiling for other machine types, I've tried it
> on a
> Dual PentiumPro, Dual PII, Dual PIII setting the CPUTYPE to the correct
> cpu
> type and the -march sticks to the assigned cpu type through all operations
> and produces nice quick optimized code.
>
> Why is this so?
>
> Is it because the "nocona" machine type optimization refers to the EMT64
> technology and thus is rejected when compiling for i386 targets rather
> than
> amd64 or emt64 targets and Gcc rejects it?

That's right. AFAIK the Nocona core is a prescott with EM64T support (feel free to correct me if I am wrong). Basically you have an i386 version of FreeBSD, and with EM64T instructions enabled GCC will build a 64-bit version of FreeBSD. I think that's the reason it switches back to prescott.

Jorn

>
> Regards
> Scott K

For the record I used "nocona" with my dual xeon emt64 2.8 GHz and it
broke my kernel.

--
Regards,

-Abdullah Ibn Hamad Al-Marri
Arab Portal
http://www.WeArab.Net/
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Relevant Pages

  • Re: gcc compiler cputype, prescott or nocona confusion
    ... This doesn't happen when compiling for other machine types, ... type and the -march sticks to the assigned cpu type through all operations ... Is it because the "nocona" machine type optimization refers to the EMT64 ... amd64 or emt64 targets and Gcc rejects it? ...
    (freebsd-questions)
  • gcc compiler cputype, prescott or nocona confusion
    ... This doesn't happen when compiling for other machine types, ... type and the -march sticks to the assigned cpu type through all operations ... Is it because the "nocona" machine type optimization refers to the EMT64 ... amd64 or emt64 targets and Gcc rejects it? ...
    (freebsd-questions)