When rebuilding an old install, the main trap is to avoid having
architectural defaults make it so you don't time your new kernel.
Follow the instructions given in Section 2.9.2,
but additionally make sure you delete any prexisting directory
that matches your ARCH definiton. Therefore, in the above
example, in the ATLAS/CONFIG/ARCHS directory, you would
rm -rf Core2Duo64SSE3
If such a subdirectory existed.
From your BLDdir directory, then issue: