Dynamical overlap fermions, results with HMC algorithm

We present results of a hybrid Monte-Carlo algorithm for dynamical, $n_f=2$, four-dimensional QCD with overlap fermions. The fermionic force requires careful treatment, when changing topological sectors. The pion mass dependence of the topological susceptibility is studied on $6^4$ and $12\cdot 6^3$ lattices. The results are transformed into physical units.