I forgot to mention - Microsoft once released a patch, WW0548.EXE, for systems with i387 FPUs.
Apparently, it was required for Windows 3.10 on 386 PCs and contained a new WIN87EM.DLL.
That dynamic link library does provide both virtualization and emulation of x87,
so multiple programs could safely make use of the math co-processor.
It is akin to WIN87EM.EXE, which was used in the days of Windows /386.
(Back then, it could be added optionally as load=win87em in win.ini.)
Anyway, 80486DX and 80486DX2 processors were excepted by that WW0548 patch..
I don't know if it was/is required for 286+287XL (i387 core) or 386+287 combos, though. 😕
Since the patch files in that self-extractor are dated mid-92, later releases of Win 3.x,
such as plain 3.11, WfW 3.10 or WfW 3.11, may already have shipped with a new DLL.
https://support.microsoft.com/en-us/help/8686 … for-intel-80387
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