Smooth scrolling on the PC was a particularly difficult problem because of design decisions made when creating PC expansion card type video systems.
Smooth scrolling, in general, was known on other hardware. That was either having enough CPU throughput and a display resolution combination that would allow the CPU to drive the display fast enough to make it happen, and or with the assistance of video display chips forming video subsystems capable of smooth scrolling by offering the kind of control needed for success, all while also leaving enough of the system resources available for a game to be made featuring the effect.
Smooth scrolling, in general, was known on other hardware. That was either having enough CPU throughput and a display resolution combination that would allow the CPU to drive the display fast enough to make it happen, and or with the assistance of video display chips forming video subsystems capable of smooth scrolling by offering the kind of control needed for success, all while also leaving enough of the system resources available for a game to be made featuring the effect.