Historically, the Mach MP work was done on an Encore system not Vaxen but I've forgotten which model and what the processor was.  I wanted to say Encore used the NS 16032, but I'm not willing to go out on a limb on that thought.   Bob Baron, Mike Accetta or Rich Rashid probably remembers.  You might look at the code for Encore support, and that might give you a hint.   FWIW:   I've lost track of Bob who was at Pitt last time I knew, but Mike is still at Microsoft.  I believe I heard Rich retired, but I'm not sure of that.   

Clem