Best options for 64-bit FP on athlon?

[Brad Lucier]

I have a lot of FP code where the algorithms depend on setting the precision
to 64-bits (i.e., no extended precision) for correctness.  Since I've
heard great things on the mail lists about MMX/SSE/SSE2/... doing
64-bit FP faster, I want to try it.

But reading the 3.1 docs, I cannot figure out what options to give to
get what I want.  Now, maybe I missed something, but I don't think
it's there.  So perhaps someone can tell me what I sould do when
/proc/cpuinfo says

flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr syscall mmxext 3dnowext 3dnow

Brad