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x86 install on athlon64 what -march setting to use?
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Rawn027
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PostPosted: Tue Apr 25, 2006 8:32 pm    Post subject: x86 install on athlon64 what -march setting to use? Reply with quote

what setting can i use to have an march that tunes for my athlon64 while using an x86 arch?
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simon_irl
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PostPosted: Tue Apr 25, 2006 9:20 pm    Post subject: Reply with quote

march=k8. it's the chost setting that determines whether x86 or 64-bit code is built. in either case, you can still optimise for your 64-bit processor.
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jmbsvicetto
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PostPosted: Tue Apr 25, 2006 10:23 pm    Post subject: Reply with quote

If your gcc version supports it, you can use -march=athlon64.
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stealthgun
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PostPosted: Tue Apr 25, 2006 10:45 pm    Post subject: Reply with quote

ive tryed this on an opteron proc, but the X86 is very slow..
dont know how it is on an Athlon64.. but the Amd64 version is a lot quicker.
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simon_irl
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PostPosted: Wed Apr 26, 2006 3:45 am    Post subject: Reply with quote

k8, athlon64, opteron and athlon-fx are all the same as far as gcc is concerned. in other words "-march=athlon64" does exactly the same thing as "-march=k8".

it's true that 32-bit code will feel sluggish if you're used to x86_64...on my amd64 systems, there was a very obvious speed difference between code compiled with chost "i686-pc-linux-gnu" and chost "x86_64-pc-linux-gnu", whereas the "march" option makes very little difference to the apps i use (so little in fact that i now build stuff for generic i686 so that i can copy the packages across to all the computers on my network, including athlon-xp's, pentiums, etc.).
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tsuehpsyde
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PostPosted: Fri Apr 28, 2006 10:58 am    Post subject: Reply with quote

Is there any reason why portage doesn't recognize k8, Athlon64, or Opteron as a valid -march?

Code:
i686-pc-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -O2 -march=k8 -pipe -fPIC -I/usr/include/python2.4 -c missingos.c -o build/temp.linux-i686-2.4/missingos.o
cc1: error: bad value (k8) for -march= switch
cc1: error: bad value (k8) for -mcpu= switch
error: command 'i686-pc-linux-gnu-gcc' failed with exit status 1

!!! ERROR: sys-apps/portage-2.0.54-r1 failed.
!!! Function src_compile, Line 47, Exitcode 1
!!! Failed to build missingos module
!!! If you need support, post the topmost build error, NOT this status message.


If I set -march=i686 and it compiles perfectly fine?
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nixnut
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PostPosted: Fri Apr 28, 2006 6:17 pm    Post subject: Reply with quote

Moved from Installing Gentoo to Duplicate Threads.
See here https://forums.gentoo.org/viewtopic-p-1309529.html#1309529
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