[The Dude]

Curtis is right not all 2 strokes need boost to fill the cylinders. But some do. Like your detroit diesels. I am a detroit diesel mechanic, i dont work on alot of two strokes but the two strokes have what you call liners (cylinders). These liners have holes on the bottom of them. When the piston uncovers these holes in the "AIRBOX" at the bottom of the stroke, booost is needed to force the charge into the cylinder because there is no difference of pressure that far down on the detroit. That is where your supercharger comes in.
A detroit 2 stroke has no intake valves these holes in the liners are the only way a charge can enter the cylinder. If you want more power you add a turbo. Detroit 2 strokes are only good for Constant High RPM, Like something you would see in a genset, but they put those darn things in firetrucks and buses. Alot of 6v71 and 92's are still out there in city buses and firetrucks.