[TUHS] Pipes and PRISM

[Paul Winalski]

On 3/1/22, Clem Cole <clemc at ccc.com> wrote:
> Btw look at Mach if you want to understand nt.  The Mach and Nt tasks are
> very lightweight and primitive so you can build much more complex processes
> from them
>
That's correct,  Dave Cutler was very impressed by Mach's microkernel
idea and used it to implement VAXeln, a VAX OS for real-time
applications (VMS had grown too heavyweight to properly support
real-time).  He used the same design for MICA and later NT.

Cutler had a lot of fights with the Windows developers.  They were
used to MS-DOS, where there was a single application running with no
memory protection, so it could do whatever it pleased as long as it
left the system in a usable state when it exited.  Windows did
cooperative multitasking and it was common practice to insert hooks to
intercept system events and procedures.  Cutler told them, no, there
will be no hooks into the NT privileged kernel--use the system service
calls provided by the NT API.  Over time, the NT microkernel and the
layers on top of it have become less distinct, but the original
concept of a microkernel with personality modules on top of it
remains.  That idea came from Mach.

-Paul W.