Combine crumbs, sugar and margarine; press onto bottom of 9-inch springform pan. Bake at 350 degrees for 10 minutes.
Combine cream cheese, sugar and vanilla, mixing at medium speed on electric mixer until well blended. Add eggs, one at a time, mixing well after each addition. Blend chocolate into 1 cup batter.
Spoon plain and chocolate batters alternately over crust; cut through batters with knife several times for marble effect. Bake at s450 degrees for 10 minutes. Reduce oven temperature to 250 degrees; continue baking for 30 minutes.
Loosen cake from rim of pan; cool before removing rim of pan. Chill.
