The components of the 3850 were new data cartridges. The data cartridges were circular  cylinders, 2 inches in diameter and 4 inches long, each holding a spool holding 770 inches of  tape. Cartridges were stored in a two-dimensional array of bins, which were hexagonal, rather  than square, to save space and, for the first time, were automatically accessed through a  robot (accessor), shown in Figure 1-13. The second generation of IBM magnetic media and the first one to use an enclosed cartridge  containing ‰-inch tape, the IBM 3480 Magnetic Tape Subsystem was announced on 22  March 1984, shown in Figure 1-14. The tape was stored in a now-familiar cartridge, which  was smaller, more robust, and easier to handle than tape reels. The cartridge capacity was  200 MB, and the channel data rate was 3 MBps, writing 18 tracks in one direction. The IBM 3490 replaced the IBM 3480 tape technology and used the same tape cartridge  media. With a tape capacity of 800 MB uncompacted (2.4 GB compressed assuming 3:1  compression ratio) and a channel data rate of 3 MBps, the IBM 3490E increased the capacity  of the 3480 four-fold. It used a double-length tape and wrote data in both directions: 18 tracks  to the end of tape and 18 tracks back to the start of the tape. Chapter 1. Tape technology introduction  15 Figure 1-14 IBM 3480 Figure 1-13 IBM 3850 1.2.8 IBM 3480 1.2.9 IBM 3490