Cream together butter and sugar. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine flour, cocoa, baking soda and salt. Gradually add dry ingredients to creamed mixture. Stir in chips and pecans. Drop by Tablespoon 2 inches apart onto ungreased cookie sheet. Bake at 350 degrees for 10 to 12 minutes or until set. Remove to wire racks.