Even with turbo set to the slower speed, on my Pentium the CD-ROM version of SQIV still ran too fast, with the sentry droid in the first area spawning every few seconds or so, making that area damn near unplayable.
It's assume that the CD version was developed alongside the floppy version and that the code forked at some point. The floppy version got the fixes, whereas the CD version didn't.
Somebody in the retro adventure gaming community with the handle NewRisingSun made a patch that used the floppy disk background images and has patched script resources to solve the myriad timing issues, whilst integrating seamlessly with the speech of the CD version.
I remember reading somewhere many, many years ago that the graphics were adjusted to have less colors to work in Windows, which reserved 20/256 colors for system use.