e fftw-3.1 release supports --enable-k7.  This option only works on
32-bit x86 machines that implement 3DNow!, including the AMD Athlon
and the AMD Opteron in 32-bit mode.  --enable-k7 does not work on AMD
Opteron in 64-bit mode.  Use --enable-sse for x86-64 machines. 

<p>
FFTW supports 3DNow! by means of assembly code generated by a
special-purpose compiler.  It is hard to produce assembly code that
works in both 32-bit and 64-bit mode.  <hr>
Next: <a href="section3.html" rel=precedes>Using FFTW</a>.<br>
