How to run FFT on multi-core without Parallel Computational Toolbox

I am using MATLAB 7.9.0(2009b) on AMD Athlon(tm) II X4 615e (4-core) processor. I am processing a code which has extensive FFT computations. I have red FFT is multithreaded function since 2008. But in my case only 1 core is in use when I run the code. Do I need something else to run on multi-cores ?