I think all it does is remove the CPU check where "Opart 4.exe" returns an error for anything older than a Pentium 4 (which happens to be what I use, Preschott). All these errors are probably due too the fractured state of operating systems and graphics accelerators these days in conjunction with this game being a Frankenstein's monster of different coding.
Actually, it changes the code. The normal code uses a separate part of the processor for doing arithmetic (floating and integer) It makes those a lot faster so should make the overall program run slower when you use the 'Slow' program. Hence the name .
Unfortunately, some of the crashes and strange behavior may be due to drivers. The coding is actually pretty clean. Norm wrote clean C code and I've updated everything to be modern C++. While not fully agile, I've been very careful to avoid side effects and use small functions. Bob Cross has also written modern C++. The reason I don't support XP is that there isn't a lot of demand. I thought that VS2017 didn't support XP since it was far past it's sell by date, but it looks like it does. I'll think about adding an unoffical and unsupported XP version.
I'm kinda surprised they're still supporting XP on the C++ side too. A few years ago they cut XP off from new versions of the .net framework to much wailing and gnashing of teeth. To be fair at the time I thought pulling the plug on XP was a bit premature, official end of life or not. Them still doing it now for C++ is a bit surprising; maybe they're keeping the C++ tools working to make things easier internally. (There's an embedded XP version still in support until April 2019.)
Did you ever see history portrayed as an old man ... weighing all things in the balance of reason?
Is not [it] an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful?