【Hitachi】 DK511-5 Magnetic Disk Unit

This disk unit used a 5.25-inch disk, and employed a voice coil motor and servo track system.
These technologies greatly reduced average seek time to 30ms—1/3 that of the previous unit.
Coated disk technology developed for large disks was applied here to a 5-inch size to achieve both high recording density and high-reliability. At the time, other companies were unable to solve the head crash problem with coated disks, and problems occurred frequently, and thus this unit was highly acclaimed in the market. Starting with this unit, the capacity of 5-inch disk units was continually enhanced for 4 generations.

DK511-5 Magnetic Disk Unit Specifications
Completion date 1983
Memory capacity per spindle 51Mbyte
BPI 9,340BPI
Surface recording density 7.3Mbit/square inc
Disk size/quantity 5.25-inch/4 disks
Head type/number per actuator Lightweight MnZn/8
Average access time 30ms
Disk rotation speed 3,600rpm
Data transfer speed 0.63Mbyte/s

DK511-5 Magnetic Disk Unit