Milpitas-based Quantum Corp claims capacity leadership in the 3.5 disk drive market with two new models in its Pro Drive line with capacities of 425Mb and 331Mb. The drives have embedded SCSI or AT-bus controllers, and average seek times of 12mS for read commands, and 14mS for write commands. The SCSI synchronous data transfer rate is up to 5Mbps, while SCSI asynchronous and AT-bus data rates are 4Mbps. They have a 64Kb cache using Quantum’s proprietary DisCache technology which reduces seek time by anticipating host requests. It claims a mean time between failures of over 75,000 hours. New features include a write caching option that speeds operation during write commands, and read-on-arrival is facilitated by servo architecture and accuracy of the data heads. Security is also enhanced by a self-testing feature, error monitoring, and Quantum’s Air lock feature for locking the head stack in the landing zone to protect data when the drive is off. Evalua tion units arrive in September with volume in November. The 425Mb vers ion will be $1,600, 330Mb, $1,350. Quantum plans a European design and manufacturing facility to complement its US and Japanese plants. It says that 1991 will see the introduction of 2.5 products, and it expects the smaller drives to erode the market share of the 3.5s in the mid-1990s.