Are you sure you don't have a rtVAX system?  The rtVAX was a 
special version of the uVAX II chip which returns a different
SID than the normal uVAX II chip.  A microVAX II should say
"MicroVAX II" but yours is not.

The only real difference between the rtVAX and normal uVAX II chip
is that the P0/P1 user page table entries must be in contiguous
physical pages instead of contiguous virtual pages according the
P0BR and P1BR cpu registers contain physical addresses instead of
virtual addresses.  This means modification to the pmap module 
would be needed.

The hard part is getting contiguous memory to handle the page tables.
At 64KB of virtual address space per physical page of PTEs, a 20 or
30MB process would require 320-480 contiguous pages of memory.  
Another has to do with supporting shared pages.  Since PTEs are always
physically addressed, sharing PTEs (such as for a shared library) is
impossible.  Unless you reserve a portion of S0 space for mapping
shared pages.
-- 
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt.html
Westford, MA              Disclaimer: I disavow all knowledge of this message