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grindz
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PostPosted: Thu Mar 07, 2013 5:57 am    Post subject: make.conf CFLAGS Reply with quote

Installing Gentoo for first time, currently configuring the make.conf file, it is telling me to use CFLAGS="-march=k8 -O2 -pipe" by default, but I just want to make sure this is right. My CPU is as follows Intel(R) Core(TM) i7 Q720 @1.60GHz

does anyone know if that is the correct switch or where i can find out?


note I am using a VM with max cores of 4


thanks in advance
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grindz
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PostPosted: Thu Mar 07, 2013 6:40 am    Post subject: Reply with quote

I found this after looking through wiki... i think this will work

CHOST="x86_64-pc-linux-gnu"
CFLAGS="-march=corei7 -O2 -pipe"
CXXFLAGS="${CFLAGS}"

http://en.gentoo-wiki.com/wiki/Safe_Cflags/Intel#Core_i7_and_Core_i5.2C_Xeon_55xx


Thanks for the help all
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khayyam
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PostPosted: Thu Mar 07, 2013 8:29 am    Post subject: Reply with quote

grindz ...

firstly, wiki-gentoo.com is not gentoo's official wiki, and the information there is not always up-to-date. As far as CFLAGS are concerned, the use of '-O2 -march=native -pipe' is recommended, gcc will then work out what optimization to use based on the information in /proc/cpuinfo. You can see what those flags will be with the following:

Code:
# LC_ALL=C gcc '-###' -e -v -march=native /usr/include/stdlib.h

or .. to just extract the flags:
Code:
# echo $(LC_ALL=C gcc -v -march=native -x c /dev/null 2>&1 | grep /dev/null | egrep -o -- '-+(m|param )\S+')

or ... for a list of all enabled/disabled target specific options:
Code:
# LC_ALL=C gcc -Q -O2 -march=native -c --help=target

HTH & best ... khay
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DONAHUE
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PostPosted: Thu Mar 07, 2013 3:24 pm    Post subject: Reply with quote

!t might be good to note that k8 is specific to AMD cpus.
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grindz
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PostPosted: Thu Mar 07, 2013 5:04 pm    Post subject: Reply with quote

Thank you all for the information. Noted on the K8 and thank you khayyam, for the valuable information. So much to learn, been primary windows for a long time... so bored with it, this is so much more challenging and fun.
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