You need the limitations of the version of windows you are using. All Windows run slow on most computers of thier release year.
Like I have my 98 running on a 2ghz proccessor, and it is lighting fast, but if I was to load something like Vista, or Seven, I am sure their would be slowdowns.
However the dos programs are very picky about hardware. They run in DOS mode, 100% of the time, but I have to enable sound, mouse drivers first. Simular to the way some PSX games request an analoug stick controller.
In windows I allways get memory errors, memory not enough, etc because windows is also using those resources up. On a 2ghz machine the DOS programs do not even see the speed, however some do see the speed, or maybe the speed is altered within the program, itself.
Windows back then was for office employees, and was resourcefull for saving white-out..... ( people who do not know a thing about computers, entering the workforce. ).
Your 486, could probably run most DOS programs, however I am sure a much later program would have problems.
The computer I had, used a list system, running windows 1-3.0 ( I forget which version. ). So when I wanted to use a dos program, I could just select from the list, at the same time I could boot into windows, and run whatever windows related program I wanted to run.
Voltage I believe, relates to hardware taking over jobs, of other hardware. Like something that, would not function like a power switch.
Try running some games in DOS, to see if any of them exibit behaviours
as with windows.