Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente. Drain and reserve.
In a large sauce pan, melt 4 tablespoons butter or margarine over medium heat. Add flour and some ground black pepper to taste; stirring until paste-like consistency. Add milk to mixture and stir continually until mixture starts to thicken; slowly stir in cheese 1 cup at a time until all cheese is melted.
Preheat oven to 350 degrees F (175 degrees C).
Pour cheese mixture over macaroni. Mix well and pour into a lightly greased 9x13 inch baking dish. Toss extra grated cheese with bread crumbs, and melt 4 tablespoons butter or margarine and mix in with cheese & bread. Spread over top. Bake in preheated oven for 25 to 30 minutes or until bubbly and golden brown. Serve.