Safe CFLAGS

Finding your CPU
To identify the model of your CPU, you can look inside for the "cpu family" and "model" numbers like so:

Once you find this information, you can then match your CPU to one listed on this page in order to find out the suggested "safe" CFLAGS.

Below you can find a list of CFLAGS which are to be considered "safe" for the given processors. These are the settings you should use if you are unsure which CFLAGS your processor needs.

Xeon E5-2407
vendor_id      : GenuineIntel cpu family     : 6 model          : 45 model name     : Intel(R) Xeon(R) CPU E5-2407 0 @ 2.20GHz

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Xeon 3040
vendor_id      : GenuineIntel cpu family     : 6 model          : 15 model name     : Intel(R) Xeon(R) CPU            3040  @ 1.86GHz

Core i3/i5/i7 with AVX2 instructions (Haswell)
vendor_id      : GenuineIntel cpu family     : 6 model          : 60 model name     : Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Core i3/i5/i7
vendor_id	: GenuineIntel cpu family	: 6 model		: 42 model name	: Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz

Core 2 Duo
vendor_id      : GenuineIntel cpu family     : 6 model          : 15 model name     : Intel(R) Core(TM)2 Duo CPU     T7500  @ 2.20GHz

Pentium M (Dothan)
vendor_id	: GenuineIntel cpu family	: 6 model		: 13 model name	: Intel(R) Pentium(R) M processor 2.13GHz

A4/A6/A8-XXXX / XXXXM
vendor_id	: AuthenticAMD cpu family	: 18 model		: 1 model name	: AMD A8-3500M APU with Radeon(tm) HD Graphics

FX-XXXX
vendor_id	: AuthenticAMD cpu family	: 21 model		: 1 model name	: AMD FX(tm)-8150 Eight-Core Processor Make sure and check the number listed by  on your system, the -march flag should be bdverX where X is the model number.

Due to the FPU design of the Bulldozer architecture, -mprefer-avx128 gives better FPU preformance at the cost of precision.

Geode LX
vendor_id	: AuthenticAMD cpu family	: 5 model		: 10 model name	: Geode(TM) Integrated Processor by AMD PCS

with optional VFPv3 FPU
Processor      : ARMv7 Processor rev 0 (v7l) processor      : 0 BogoMIPS       : 1987.37

processor      : 1 BogoMIPS       : 1987.37

Features       : swp half thumb fastmult vfp edsp thumbee vfpv3 vfpv3d16 tls CPU implementer : 0x41 CPU architecture: 7 CPU variant    : 0x1 CPU part       : 0xc09 CPU revision   : 0

Hardware       : Toshiba AC100 / Dynabook AZ Revision        : 0000 Serial         : 0000000000000000

ARMv6/ARM1136JF-S
Processor      : ARMv6-compatible processor rev 5 (v6l) BogoMIPS       : 791.34 Features       : swp half thumb fastmult vfp edsp java CPU implementer : 0x41 CPU architecture: 6TEJ CPU variant    : 0x1 CPU part       : 0xb36 CPU revision   : 5

Hardware       : IMAPX200 Revision       : 0000 Serial         : 0000000000000000

Not in the List
Try the following command to see if you will see something useful.

You will get something like below...

Notice the -march reply?

Get this from gentoo forums. Illegal Instruction with Xeon E5-2630L

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