On Tue, 2010-01-05 at 06:24 -0800, Bob Armstrong wrote: Anyway it seems that whenever I run Personal Alpha any Simh machines I have running completely pause until I shutdown the Alpha simulator has anyone else had this problem ? Isn't Personal Alpha a version of the Charon-AXP emulator? I've never used Personal Alpha, but I am using the free version of Charon-AXP and I can tell you that, unlike simh, it has no OpenVMS idle detection. Charon will always use 100% of whatever CPU(s) it's running on, regardless of what the emulated system is doing. That makes it difficult to run Charon concurrently with other simulators unless you can afford to dedicate separate CPUs to each one. Bob -- ... and significantly bumps up your electricity bill to boot.