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Comment by MarkSweep | Hacker News Reader

If you include the ability of 32-bit versions of Windows to run 16-but Windows and DOS applications with NTVDM, it is more like 40+ years.

https://en.wikipedia.org/wiki/Virtual_DOS_machine

(Math on the 40 years: windows 1.0 was released in 1985, the last consumer version of Windows 10 (which is the last Windows NT version to support 32-bit install and thus NTVDM) goes out of support in 2025. DOS was first released in 1981, more than 40 years ago. I don’t know when it was released, but I’ve used a pretty old 16-bit DOS app on Windows 10: a C compiler for the Intel 80186)

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> I’ve used a pretty old 16-bit DOS app on Windows 10: a C compiler for the Intel 80186

It’s amazing that stuff still runs on Windows 10. I’m guessing Windows 10 has a VM layer both for 32-bit and 16-bit Windows + DOS apps?

Windows 10 only does 16-bit DOS and Windows apps on the 32-bit version of Windows 10, so it only has a VM layer for those 16-bit apps. (On x86, NTVDM uses the processor's virtual 8086 mode to do its thing; that doesn't exist in 64-bit mode on x86-64 and MS didn't build an emulator for x86-64 like they did for some other architectures back in the NT on Alpha/PowerPC era, so no DOS or 16-bit Windows apps on 64-bit Windows at all.)

https://github.com/leecher1337/ntvdmx64

True. I just assumed that 16-bit support got dropped since Windows 11 was 64-bit only.

Microsoft decided not to type "make" for NTVDM on 64-bit versions of Windows (I would argue arbitrarily). It has been unofficially built for 64-bit versions of Windows as a proof-of-concept: https://github.com/leecher1337/ntvdmx64

That’s okay, and if people want to test their specific use case on that and use it then great.

It’s a pretty different amount of effort to Microsoft having to do a full 16 bit regression suite and make everything work and then support it for the fewer and fewer customers using it. And you can run a 32 bit windows in a VM pretty easily if you really want to.

Or you can run 16-bit Windows 3.1 in DOSBox.

Sure, but again that’s on you to test and support.

> Microsoft decided not to type "make" for NTVDM on 64-bit versions of Windows (I would argue arbitrarily).

I recently discovered that Windows 6.2 (more commonly known as Windows 8) added an export to Kernel32.dll called NtVdm64CreateProcessInternalW.

https://www.geoffchappell.com/studies/windows/win32/kernel32...

Not sure exactly what it does (other than obviously being some variation on process creation), but the existence of a function whose name starts with NtVdm64 suggests to me that maybe Microsoft actually did have some plan to offer a 64-bit NTVDM, but only abandoned it after they’d already implemented this function.

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