OK, so problem is solved.But I suspect it multitasks
differently on
different hardware, unless You use existing V7 x86 implementation. I do
not know pdp architecture, I suspect it does differ from x86, I mean
TSS,GDT, TR etc.
These details are hidden under the kernel. The idea of a process with
address space and other contexts are what V7 provides. It's pretty
easy to implement what V7 expects using Intel's paging.
Brantley