【Hitachi】 H-8577 Grouped Magnetic Disk Drive

The H-8577 disk drive was developed as a high-capacity magnetic disk unit for Hitachi mainframes.
This unit was positioned as the main disk for online computers in the early 1970s.
The basic system of this unit was derived from the H-8564 magnetic disk drive, but the surface recording density was doubled, and the number of disks comprising the disk pack was increased to 11, so the capacity per spindle was greatly increased to 30Mbyte. A grouped disk unit was configured by equipping these disk packs with 9 spindles per controller (including spare disks), and thus memory capacity per controller increased dramatically.
For the recording media, a disk pack was configured from eleven 14-inch coated disks, and the number of heads was doubled to 20. The worsening of positioning accuracy due to the increased number of heads was resolved by improving the precision/management of each mechanism.
The same hydraulic mechanism/FM recording system as in previous equipment was used as the actuator/recording system.
This unit had media compatibility with the IBM2314 disk unit, and disk packs could be exchanged between the two.

H-8577 Magnetic Disk Drive Unit Specifications
Completion date May 1970
Memory capacity per unit 60Mbyte/DKU
Memory capacity per spindle 30Mbyte
BPI 2,200BPI
Surface recording density 0.22Mbit/square inch
Disk size/quantity 14-inch/11disks
Head type/number per actuator Heavyweight inductive/20
Average access time 75ms
Disk rotation speed 2,400rpm
Data transfer speed 300Kbyte/s

H-8577 Grouped Magnetic Disk Drive