<page_title> History of IBM CKD Controllers </page_title> <section_title> Chronological summary </section_title> <table> <cell> 3880-11, 13 SCU </cell> <cell> dual directors, large cache </cell> <cell> 3880-21, 23 SCU </cell> <cell> dual directors, large cache </cell> </table>
Models 3880-11, 3880-13, 3880-21, and 3880-23 have dual directors.