In September 1987, IBM announced a significant extension to the 3380 series: the Model K DASD that stored 7.5 billion characters of information, and the densest disk device IBM ever manufactured; and the high-speed Model J, which could locate data faster than any previous 3380 DASD. The Model J found the correct information track in an average time of just 12 thousandths of a second. Customers who installed Model Js, which could store 2.5 billion characters of data, could upgrade it to the denser Model K.

Also announced at the same time was the new 3380 Direct Channel Attach Model CJ2 -- which combined new 3380 DASD technology and new storage control function in one unit.

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Among the technological enhancements that extended the capabilities of the three new 3380 DASDs compared with their predecessors was a sophisticated head positioning mechanism that significantly reduced the minimum amount of time it took to locate data. The new DASDs could be attached to an appropriately configured IBM 3880 Storage Control and a new IBM 3990 Storage Control. Several configurations of the new DASDs also could attach to the new 3380 Model CJ2. Integrating the control function and 1.26 billion characters of disk storage in one unit made the Model CJ2 highly cost-effective. At the time, the CJ2 was IBM's lowest price 3380 disk storage subsystem for many customers, especially those with intermediate systems.

The new 3380 subsystems saved about 50 percent in floor space and about 33 percent in electricity and air conditioning compared with previous IBM storage subsystems configured with similar capacity.

The cost of storing information was also reduced. For example, the new 3380 Model K offered 50 percent more storage for only a slightly higher price than IBM's densest current 3380.

The new 3380 Models J and K were scheduled to be available in October 1987, and the 3380 Model CJ2 was scheduled for shipment in the third quarter of 1988.