I have recently installed a new dual P4 Xeon system. For a particularly computeintensive program I have been advised to turn of hyperthreading in the BIOS, so now Linux sees two CPUs instead of four logical CPUs - makes sense :-) I know that the binding of a process to a cpu is "loose" under linux (as apposed to Irix say) and one expects jobs to hop between CPUs every now and then. But I have been monitoring (via top) a simple perl script (no forks or threading involved) and not only does it switch CPU, sometimes it seems to split accross the CPUs with 50% utilization on each CPU, or even a 25/75 split. I have never noticed this before on dual CPU machines (I have a few dual PIIIs). The machine is still running the SuSE supplied SMP kernel: Linux version 2.4.18-64GB-SMP (root@SMP_X86.suse.de) (gcc version 2.95.3 20010315 (SuSE)) #1 SMP Wed Mar 27 13:58:12 UTC 2002 Please enlighten me. -- Simon Oliver