Date: Wed, 31 Jan 2007 16:59:09 +0000 From: "Abdullah Ibn Hamad Al-Marri" <almarrie@gmail.com> To: "Jorn Argelo" <jorn@wcborstel.com> Cc: Scott Killen <salkillen@internode.on.net>, freebsd-questions@freebsd.org Subject: Re: gcc compiler cputype, prescott or nocona confusion Message-ID: <499c70c0701310859g6bfca627t794e8b6a5580820c@mail.gmail.com> In-Reply-To: <209e855bb68d64550ec4e384b3983664@mail.wcborstel.com> References: <200701312340.38593.salkillen@internode.on.net> <209e855bb68d64550ec4e384b3983664@mail.wcborstel.com>
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On 1/31/07, Jorn Argelo <jorn@wcborstel.com> wrote: > > > On Wed, 31 Jan 2007 23:40:38 +1100, Scott Killen <salkillen@internode.on.net> 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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