【Hitachi】 DK811-4 Magnetic Disk Unit

This 8-inch disk unit was marketed as an OEM disk unit for office computer manufacturers.
Since the unit employed a voice coil motor system as a head positioning mechanism, instead of the previous step motor, seek time was greatly increased to 25ms.
The HDA (Head Disk Assembly) had a completely sealed structure, and thus had outstanding environmental resistance and required no periodic maintenance.

DK811-4 Magnetic Disk Unit Specifications
Completion date 1980
Memory capacity per spindle 47Mbyte
BPI 7,300BPI
Surface recording density -
Disk size/quantity 8-inch
Head type/number per actuator -
Average access time 25ms
Disk rotation speed 3,521rpm
Data transfer speed 0.9Mbyte/s

DK811-4 Magnetic Disk Unit