This was a hard disk unit employing a 20cm (8-inch) magnetic disk, announced by Mitsubishi Electric in 1980. There were two models -- one with a 21MB memory capacity and one with a 50MB memory capacity. In response to the growing demand for files in minicomputers, office computers, microcomputers and various types of terminals, this system was developed to diversify and increase the capacity of external memory units, and at the same time to achieve greater compactness, ease of connection and lower price.
This unit had the following features:
- It achieved high-capacity while retaining a compact design.
- Technology from large magnetic disk units was applied to enable high-density memory, and high speed, high precision and high reliability were achieved by using a track-following servo system employing a linear motor.
- The unit achieved the same level of RAS (Reliability, Availability, Serviceability) as large magnetic disk units by using LSI technology.
- The unit could be set up horizontally or vertically, and had the same width as a flexible disk unit. Therefore, it was possible to mount 2 units side-by-side in a 19-inch standard rack.
- The effects of external dust were eliminated by using a completely sealed structure.
- The unit used the SMD and TRIDENT industry-standard interfaces, and thus could be connected easily, and used together with previous models.
- The affects of differences in power supply frequency were eliminated by using DC brushless motors.
- There was no need for periodic maintenance.
|Unit memory capacity||21.73MB(model 1),50.71MB(model 2)|
|Number of disks||2(model 1),4(model 2)|
|Recordable sides||3 sides(model 1),7 sides(model 2)|
|Number of tracks per side||539|
|Data transfer speed||6.45Mbit/s(806Kbyte/s)|
|Positioning time||Min.10ms,Max. 60ms,Average 35ms|
|Rotational delay||Average 8.33ms|