[anyfoo]

> I don't really recall extended memory ever being used much on PCs running a real mode operating system like DOS.

Extended Memory/XMS was pretty much a DOS thing, though. Anything using protected mode would not need it, and be able to just access the memory directly.

> that weren't really made unnecessary until Windows 3.0 (or other OSs with a protected mode)

Windows 3.0 was "sort of" a protected mode OS. The actual Windows part ran as a 16bit task, similar to DOS in EMM386. That changed, again "sort of", with Windows 3.1. There was a thing called "Win32s" to run 32bit Windows applications, but most of Windows was still a single 16bit task.

Windows NT was the real deal, though, shedding off its real mode roots with essentially a reimplementation. It only became part of the "mainstream" Windows versions with Windows XP (Windows 2000 was based on NT already, but still marketed alongside the "legacy" Windows 95/98/ME).

[efrecon]

I have a VERY vague memory that you could copy win32s from 3.1 into 3.0 to help running 32bit apps there. There might have been some fiddling with some sys.ini involved. But I might just be dreaming awake or something...

[anyfoo]

I can imagine that you're right! Would not be too surprising if Win32s was self-contained enough, and the differences between 3.0 and 3.1 small enough (although there were larger ones at least in some other aspects), that this could be done reasonably. (Though most apps were still likely to be 16 bit apps at that time, so not making any use of Win32s.)