In old NuBus times, several graphics cards had an extended desktop. Their driver told the OS the screen would be, say 2048*768 instead of the 1024*768 pixels the monitor would show.
When you moved the mouse near the left or right edge of the shown 1024 pixel wide "window", the underlying 2048 pixel wide desktop would scroll smoothly... Scrolling was performed by the graphics hardware - the running applications never knew that the real screen was smaller than the virtual screen. The BIG advantage over todays desktop managers: It also works with applications which do not cooperate or (for developers) are just being debugged.
If that was possible 10 years ago with 4MB graphics cards, why can't todays 256MB graphics cards do the same?
Review: Desktop Manager