[josefx]

Old windows programs had the luck that intel fucked up Itanium, which left us with AMDs idea to just take the existing 16 bit compatible 32 bit processor and turn it into a 32 bit compatible 64 bit processor (that might also be 16 bit compatible, not sure on that one). As result new and old windows programs use a lot of the same basic instructs and emulating the newer programs includes a lot of the work needed to also emulate the older ones.

[kbolino]

Modern x86-64 processors are still capable of running 16-bit code but, assuming you want to do it from within a modern operating system, it needs to be 16-bit protected-mode code, which isn't that useful since I think most 16-bit games run in real mode. Hence why DOSbox/Bochs are used instead (also, for emulating the original sound/graphics hardware).

AFAIK, no 64-bit version of Windows ever shipped with native 16-bit support, though. That means 16-bit support on x86-64 in practice was only ever usable on a 32-bit operating system, which means you still couldn't have 64-bit, 32-bit, and 16-bit code running side-by-side, even if the hardware could theoretically support it.

Intel does want to get rid of most of the compatibility modes, including all 16-bit support, but they haven't done it yet: https://www.intel.com/content/www/us/en/developer/articles/t...