Hi.  The answers to my question about memory locations piqued my curiosity
now.  I know that under MacOS, the processor always runs in Supervisor
mode.  Under NetBSD, does it run in User Mode until an interrupt is called
to give protected memory?
My next question is: Are ROM Toolbox calls made under NetBSD without
breaking the pre-emptive multitasking of UNIX? If the multitasking does get
broken by calling utilities like _ADBOp, how is this handled by NetBSD?  Is
there a significant performance or reliability penalty?
I'm just trying to get an idea of how the memory map and set-up of the
processor for running NetBSD may affect how some machines may behave under
NetBSD, notably machines with weird configurations or undocumented video
hardware, such as the LC 475, Q 605, Q 950, IIfx, et al.
Would setting up future kernels to use Apple's memory maps under NetBSD
break NetBSD completely, or would minor source changes fix the chaos?

Thanks for the great answers,
Steve