[TUHS] Windows roots and Unix influence (was Re: Happy birthday, Ken Thompson!)

Paul Winalski paul.winalski at gmail.com
Tue Feb 6 05:43:33 AEST 2018

On 2/4/18, Wesley Parish <wobblygong at gmail.com> wrote:
> From what little I know, Dave Cutler was wanting to work on a VMS
> (Next Generation) at DEC, but couldn't manage to get management to
> agree, so when the possibility of doing a VMS (Next Gen) at Microsoft
> came up, he jumped for it.

By the mid-to-late 1980s, advances in CPU technology tilted the
performance field in favor of RISC architectures vs. complicated CISC
such as VAX or x86.  Both DEC and Intel were looking for alternatives.
Intel eventually settled on a VLIW architecture that became Itanium.
DEC's first attempt at a VAX successor was a RISC architecture called
PRISM.  It was developed by Dave Cutler's team in Seattle.  On the
software side, they were working on an OS called MICA.  It was to be a
successor to the VAXeln microkernel-based realtime system and was to
have both VMS and Unix kernel interfaces (personality modules).

Someone (Gordon Bell, I think) once said of DEC's decision making
process, "any decision worth making once is worth making again".  In
typical DEC fashion, another RISC architecture was designed by DEC's
east coast engineering team.  This architecture eventually ended up
being called Alpha.  The east coast won the political battle.  PRISM
and MICA were cancelled.  The idea of a single kernel with multiple OS
personalities was dropped; VMS and Unix were ported separately to

After PRISM was cancelled, Dave Cutler left DEC and went to Microsoft
as architect for their new OS.  Under the covers, the original Windows
NT looked a lot like MICA, VAXeln, and VMS before it.  Not surprising
since they shared the same designer.  Like MICA, Windows NT was
microkernel-based, with OS personality modules layered on top.  There
were two of these originally:  Win32 and POSIX.  Microsoft and Intel
were having a little lover's quarrel at the time--Intel didn't like
Microsoft's forays into the hardware side of things with Xbox and the
like; Microsoft wasn't pleased by Intel doing its own compilers, etc.
This led to Microsoft porting Windows NT to both PowerPC and Alpha.
Neither port caught on in the marketplace.

-Paul W.

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