MATLAB seems to use multiple cores and threads but not processors

Hi

I have a computer with 2 processor, 10 cores each, 2 threads per core. When I run say a big matrix multiplication the windows task manager shows me that matlab uses 50% of the computers CPU capacity.

If I do the same on a standart 1 CPU,4 Core, 2 threads per core computer matlab uses 100% of the capacity.

So it seems matlab just uses one processor.

I guess it doesn't matter, but the parallel toolbox is available. Changing maxnumthreads from default (20) to 40 doesnt change anything.

Any idea what I have to do to make full use of the multi processor computer?

Many Thanks! Best Dominik