For optimal performance you should rebuild the source rpm on your own system. You first need to disable cpu frequency scaling,
assuming your hardware supports this. Install the cpufrequtils package and do (for a dual core cpu)

sudo cpufreq-set -c 0 -g performance
sudo cpufreq-set -c 1 -g performance

After installing your binary rpm, test the atlas libraries by going to rpm/BUILD/atlas-g95-3.8.0/build and doing

make check
make ptcheck
make time

For more testing, unpack the file /usr/lib64/g95/packages/lapack-3.1.1/lapack_tests.tgz in a convenient location
then replace the lapack test script with the atlas one, as follows:

cd lapack_tests
rm dotests
cp /usr/lib64/g95/packages/atlas-3.8.0/dotests .
sh dotests

(On 32 bit systems, 'lib64' will be just 'lib'.) Alternatively, follow the instructions in

/usr/share/doc/packages/atlas/3.8.0/TestTime.txt

Before your CPU melts down, you should then do

cpufreq-set -c 0 -g ondemand
cpufreq-set -c 1 -g ondemand