Ah, x64 aka x86-64, AMD64 - was basically a conspiracy between AMD and Microsoft to sell unneeded upgrades and pull the wool over consumers' eyes. The average person never did and still doesn't have any need for 64-bit (to the extent that it seems so, it's only because some applications have been optimised for it), and the specification with no reason whatever broke compatibility with 16-bit programs, real mode, and DPMI. The fact that it prohibits use of segment registers except in the very way that Windows uses them is all you need to know. Intel not then being in Microsoft's pocket did things right with Itanium.
I'll continue to use SoundFX, then, and it should work from my own DJGPP programs, which I will be testing shortly. I don't care if it stole code, not being a GPL 'believer'. (That's another topic ...)
Though this isn't the DOSBox forum, I'll cite three problems (other than speed) DOSBox has that NTVDM doesn't:
- Can't display 320x200 in correct aspect ratio, even though hardware supports it
- Can't use _real_ PC speaker instead of emulation
- Gets refresh rate wrong for 640x480 VGA using 70 Hz (instead of 60),
which causes my monitor to overscan
All three are egregious.