[emily-c]

Before VMS there was the family of RSX-11 operating systems which also had ASTs (now called APCs in NT parlance), IRPs, etc. Dave Cutler led the RSX-11M variant which significantly influenced VMS. The various concepts and design styles of the DEC family of operating systems that culminated in NT goes back to the 1960s.

It's sad that the article didn't mention VMS or MICA since NT didn't magically appear out of the void two years after Microsoft hired the NT team. MICA was being designed for years at DEC West as part of the PRISM project.

[rbanffy]

In many ways NT was a new, ground up implementation of “VMS NT”.

It started elegant, but all the backwards compatibility, technical debt, bad ideas, and dozens of versions later, with an endless list of perpetual features driven by whoever had a bigger wand at Microsoft at the time of their inception, takes a toll. Windows now is much more complicated than it could be.

It shocks me some apps get Windows NT4 style buttons even on Windows 11.

[emily-c]

>In many ways NT was a new, ground up implementation of “VMS NT”.

Most definitely. There was a lot of design cleanup from VMS (e.g. fork processes -> DPCs, removing global PTEs and balance slots, etc), optimizations (converging VMS's parallel array structure of the PFN database into one), and simplification (NT's Io subsystem with the "bring your own thread" model, removing P1 space, and much more). SMP was also designed into NT from the beginning. You can start seeing the start of these ideas in the MICA design documents but their implementation in C instead of Pillar (variant of Pascal designed for Mica) in NT was definitely the right thing at the time.

[heraldgeezer]

>It shocks me some apps get Windows NT4 style buttons even on Windows 11.

This is good, though. The alternative is that the app won't run at all, right? Windows NT is good because of that background compatibility, both for business apps and games.

[radicalbyte]

Under Windows it's very rare to have trouble to running software. When you have trouble it's usually due to some security considerations or because you're using something which has roots in other operating systems.

MacOS & Linux are nothing like this. You can run most software, as most of the basis for modern software on those stacks is available in source form and can be maintained. Software which isn't breaks.

Apple/Google with their mobile OSes take that a step further, most older software is broken on those platforms.

The way they've kept compatibility within Windows is something I really love about the platform.. but it I keep wondering if there's a way to get the best of both worlds. Can you keep the compatibility layer as an adhoc thing, running under emulation, so that the core OS can be rationalised?

[markus_zhang]

How do you get Windows NT4 style buttons on 11? That's something I want to do with my application!

[TheAmazingRace]

Fun fact. If you increment each letter of VMS by one, you get WNT. If that isn't on purpose, it's a convenient coincidence.

[Taniwha]

Vaxes also had hardware support for ASTs in VMS (unlike NT) - they were essentially software interrupts that only triggered when the CPU was in a process context and no enabled interrupts were pending - so you could set a bit in a mask in another thread's context that would get loaded automatically on context switch and triggered once the thread was runnable in user mode .... device drivers could trigger a similar mechanism in kernel mode (and the 2 intermediate hardware modes/rings). There were also atomic queue instructions that would dispatch waiting ASTs

[ssrc]

Months ago I found this presentation on youtube, "Re-architecting SWIS for X86-64"[0], about how VMS was ported from VAX to Alpha to Itanium to x86 that did not have the same AST behaviour.

[0] https://www.youtube.com/watch?v=U8kcfvJ1Iec

[jdougan]

Especially since there was, apparently, MICA code copy pasted verbatim in NT.

https://www.techmonitor.ai/technology/dec_forced_microsoft_i...

I was wondering for years why MS continued to support DEC Alpha CPUs with NT.

[rasz]

Didnt it end brilliantly for MS? Settlement involved MS supporting Alpha while DEC trained its enormous sales/engineering arm to sell and support NT thus killing any incentives to buy DEC hw in the first place. DEC moved upstream the value chain and Microsoft moved tons of NT to all existing DEC corporate customers.