Hey Michael, Thanks for the article, Correct me if I'm wrong, but I was under the impression that trips to kernel land were not expensive within the BeOS, since the kernel area was mapped into the lower portion of every process's memory area, and therefore trips to kernel land do not require a context switch but merely a switch in and out of x86 protected mode. . . Also your article kinda reminded me of the following link about freebsd's copy on write implementation, if you haven't seen it before you'll probably find it interesting: http://www.daemonnews.org/200001/freebsd_vm.html Cheers, -Steffen