[zwieback]

Great question and a puzzler for me at first. From my perspective only expanded memory mattered (bank-switched block in memory space < 1MB) because all the apps I was using at first didn't support extended memory, which requires some switching to protected mode and the effort to add that to real mode programs was high.

It's extra confusing because initially expanded memory was done with add-on cards and later extended memory drivers (on 286 and up) could emulate expanded.

[ghaff]

I don't really recall extended memory ever being used much on PCs running a real mode operating system like DOS. I definitely had an expanded memory add-on board at one point though.

There were a lot of essentially kludges in the latter days of DOS that weren't really made unnecessary until Windows 3.0 (or other OSs with a protected mode) and the 80386 and later processors.

[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.)