Nowadays, powerful parallel SAT solvers are based on an algorithm portfolio. Thealternative approach, (iterative) search space partitioning, cannot keep up, although, ac-cording to the literature, iterative partitioning systems should scale better than portfoliosolvers. In this paper we identify key problems in current parallel cooperative SAT solvingapproaches, most importantly communication, how to partition the search space, and howto utilize the sequential search engine. First, we improve on each problem separately. Ina further step, we show that combining all the improvements leads to a state-of-the-artparallel SAT solver, which does not use the portfolio approach, but instead relies on it-erative partitioning. The experimental evaluation of this system completely changes thepicture about the performance of search space partitioning SAT solvers: on instances ofa combined benchmark of recent SAT competitions, the presented approach can keep upwith the winners of last years SAT competition. The combined improvements improve theexisting cooperative solver splitter by 24%: instead of 561 out of 880 instances, the newsolver Pcasso can solve 696 instances.