CPU	Family	Rec. system gcc	Rec. ports compiler
Intel Atom D525	atom	CPUTYPE=core2 (*)	gcc45 -march=atom
Intel Xeon 3065	core2	CPUTYPE=core2 (*)	gcc45
Intel Xeon E5310	core2	CPUTYPE=core2 (*)	gcc45 -march=core2
Intel Xeon E5405	core2	no CPUTYPE	gcc45 -march=core2
Intel Core i7-920	nehalem	CPUTYPE=nocona	gcc45 -march=nocona
Intel Xeon X3450	nehalem	CPUTYPE=nocona	gcc45 -march=nocona
Intel Xeon E5620	nehalem	CPUTYPE=nocona	gcc45 -march=nocona
AMD Opteron 6128	barcelona	CPUTYPE=opteron-ssse3	gcc45 -march=barcelona

http://blog.vx.sk/archives/25-FreeBSD-Compiler-Benchmark-gcc-base-vs-gcc-ports-vs-clang.html