Date: Thu, 01 Feb 2007 20:55:26 +0100 From: Jorn Argelo <jorn@wcborstel.com> To: Garrett Cooper <youshi10@u.washington.edu> Cc: freebsd-questions@freebsd.org Subject: Re: gcc compiler cputype, prescott or nocona confusion Message-ID: <45C245AE.6020308@wcborstel.com> In-Reply-To: <45C1593C.8050003@u.washington.edu> References: <200701312340.38593.salkillen@internode.on.net> <209e855bb68d64550ec4e384b3983664@mail.wcborstel.com> <45C1593C.8050003@u.washington.edu>
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Garrett Cooper wrote: > Jorn Argelo 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. > > Most of the time you're right. However (for starters), some nocona > chips feature 2MB cache instead of 1MB cache: > > <http://www.anandtech.com/IT/showdoc.aspx?i=2447&p=2>. > > I'd have to look more in depth, but OTOH the nocona also featured some > architecture upgrades, other than just the "64-bit'ness" > > I heard that gcc 3.4.x was pretty funky with the nocona processors > though, and prescott's a more stable target; that changed a bit in gcc > 4.x I think. Or maybe I'm just mixing up nocona and yonah in this case. > -Garrett > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "freebsd-questions-unsubscribe@freebsd.org" > Yonah is the Pentium M version of the first Core generation I believe. Or maybe it was still a Netburst, I can't remember. Jorn
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