English: The Cromemco XXU processor board, introduced in 1986, was the fastest CPU ever developed for the S-100 bus. It used a Motorola 68020 processor with 68881 co-processor operating at 16.7 MHz. It also had a 16 Kbyte high-speed cache memory. This CPU was used in the Cromemco CS-250 computer, widely deployed by the U.S. Air Force.