Preheat oven to 350 degrees F (175 degrees C). Grease a 2 quart baking dish.
Cook macaroni according to package directions; drain.
In a large saucepan, melt butter over medium heat. Stir in flour, salt and pepper until smooth. Gradually stir in milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Reduce heat; stir in 1-1/2 cups cheese until melted. Remove from the heat.
Stir macaroni into cheese sauce. Spoon into prepared baking dish. Sprinkle with remaining cheese and bacon.
Bake 25 minutes in the preheated oven, or until bubbly and lightly browned.