A dual processor machine of mine with Opteron 246s just downloaded a new version of hadsm3, 4.13. Seconds per timestep went up from 2.0x (4.11, 4.12) to 2.60 (two hours more per trickle). By the way, I never had any stability problems with any of the previous versions (4.04, 4.11 and 4.12 all run fine for me).