This. I was recently backing up some stuff from an old Mac OS 8 machine and it was amazing how snappy a lot of things feel. But if something is not on RAM you can clearly notice it.

Ah, I remember those days. Around that era, dragging windows around the screen was switching from "draw outline" to "draw the actual window".

I wish I could switch to outline. I don't know why people demand to see the contents of the window while dragging, it's not like it's usable or you can even read anything... and it could save some cpu cycles.

At least at the beginning not everybody had hardware that supported DMA for disk access (and those that had it, not always had it configured properly).

That meant burning CPU cycles just for doing IO.

Drawing to the screen was also slow until accelerated 2D cards came along.