I tried the QS H2O-256 benchmark, and cp2k on 2 cpus is even slower. 1 cpu = 22579 secs 2 cpus = 24942 secs The em64t is equipped with 8MB of ram. Don't know if this can be a bottleneck with 256 waters. Anyone having some bechmark ? Also absolute execution time, 1 cpu is wellcome Thanks Luigi