  We report on simulations with two flavors of O(a) improved degenerate Wilson
fermions with Schroedinger functional boundary conditions. The algorithm which
is used is Hybrid Monte Carlo with two pseudo-fermion fields as proposed by M.
Hasenbusch. We investigate the numerical precision and sensitivity to
reversibility violations of this algorithm. A gain of a factor two in CPU cost
is reached compared with one pseudo-fermion field due to the larger possible
step-size.
