Ultrix for DECstations - test-drb@ccmp.vtda.org

10 Nov 2005

...

Subject: Re: Ultrix for DECstations
   From: Paul Koning <pkoning at equallogic.com>
   Date: Thu, 10 Nov 2005 13:17:36 -0500
     To: cctalk at classiccmp.org

 >>>> "Patrick" == Patrick
Finnegan <pat at computer-refuge.org> writes: 
 Patrick> No, those were "DEC 3000"s.  DECstations (3000/5000/etc)
 Patrick> were all MIPS.

 Patrick> And, from what I've heard, at least one reason that DEC made
 Patrick> Alpha, and didn't port VMS to the MIPS architecture, is
 Patrick> because they'd have to make a lot of changes to VMS, because
 Patrick> of its security model, in order to make it work with MIPS.
 Patrick> Aparently, MIPS just didn't work enough like a VAX CPU to
 Patrick> easily port VMS to it.

Maybe.  But I wonder what could be missing that Alpha has and MIPS
doesn't that is so critical. 
An advantage over VAX.  At that point in time it was considered but 
the forward planning people already had strong feeings that the VAX
killer machine was to be next generation and generally that meant
larger address (more than 32bits).

...
 Supposedly, the only reason MIPS has supervisor mode is
that DEC
insisted on having it added. 
I'd heard that.  Never able to verify it.

Allison