Yeah, you can build customized hardware on PC or Amiga or Minimig, but we were talking about using standard PC (what most people have out there). So that if you wrote a game, you can estimate that joystick reading will take 1.8 microseconds or something like that.
But your whole argument is that the PC does NOT have the necessary standard hardware and that the Amiga does, so it is better. Therefore you cannot argue against customised hardware as according to you, its the only way the PC can compare to the Amiga.
I fail to see how any of this applies to modern game programming. Your whole argument has been that the Amiga joyport is good because it can do things that are completely useless for game programming. Why would a game need to record EXACT joystick actions? It doesn't. If it was any use, PCs would still be able to do it. Games consoles use Bluetooth and other variable latency inputs which are perfectly fine for gaming. Arguing that having lower latency, being able to probe them quicker, would actually be of any benefit at all, is silly.
No, there's no multitasking needed if application runs going directly to hardware. Application can take over the timer interrupt that OS is using for multitasking so OS won't be multitasking. As I stated, see Amiga as an example of a computer that does this. OS supports multitasking applications but it also supports single tasking applications that can use hardware fully to get the task done most efficiently.
Now you are talking about single tasking? Guess what, even games consoles are multitasking, multi-threaded computers. Surely the kind of hardware banging you are talking about makes even DMA really tricky - how would you ever pull those textures in? The whole point of modern programming is you have different helper threads which can deal with various parts of your game, be written by different developers, but all interact with each other for the end product. So again, I fail to see how your arguments have any bearing in reality.