AF-S lenses don't have the screw-slot to manually drive the AF.
When you talk about camera's AF motor, it refers to this rotating screw slot on the camera side's lens mount. It rotates and drives the AF in the lens.
For AF-S, it is electronic signal sent from camera to lens, using the lens's motor, thus no rotating slot on the lens itself.
I think one of the new models, D60 or something does not have the screw slot, so it can only AF with AF-S lenses, and normal AF lenses can only be used in manual focus mode.