Preheat oven to 350 degrees F (175 degrees C). Grease and flour 3 - 8 inch round pans.
In a large bowl cream 1/2 cup margarine until smooth. Blend in the eggs. Add the cake mix and crushed pineapple with juice and mix until smooth. Stir in the 1/2 cup chopped pecans.
Pour batter into prepared pans. Bake in the preheated oven for 20 to 30 minutes, or until a toothpick inserted into the centers of the cakes comes out clean. Allow to cool.
To make the frosting: In a medium bowl cream 1/2 cup softened margarine and the cream cheese until smooth. Gradually blend in the confectioners' sugar and 1/2 cup chopped pecans.