Sorry should've been more clear- it's more like the translation of the routes is slow. This is because you have to take all the floating point waypoints from Street Atlas or whereever, find the minimum,maximum points, find the center point, and then project all the points around the center in integer distances.
This probably could be optimized though, I remeber back in the day people pulled all kinds of tricks to run 3d programs on CPUs with lousy FPUs- fixed-point math comes to mind. Still this wouldn't be an easy project..