The M2225 magnetic disk unit was a Fujitsu magnetic disk unit for OEM which employed a 3.5-inch disk. It was completed in January 1987. This unit was jointly developed by Nippon Peripherals Ltd. (NPL, Fujisawa)—a joint venture of Fujitsu and Hitachi—and Fujitsu was in charge of manufacturing and sales.
3.5-inch magnetic disk units became common together with the personal computers which began to appear in the latter half of the 1980s.
This unit had the following features:
- 1) External dimensions were based on installation in a personal computer, and were set to half those of the 5.25-inch drive.
- Mechanisms were simplified and miniaturized by, for example, using a direct drive DC motor for spindle rotation and a stepping motor for driving the magnetic head.
- 2) Annual recording density improvements of almost 100% were achieved by exploiting the technological synergy between 8-inch and 5.25-inch, and adopting a state-of-the-art access head and disk media.
- 3) Compatibility with many types of interface
- The unit was compatible with many types of interface: the SA type for SASI, the AD type for ST506/ST412, the DR type for ST506GR, the S type for SCSI and the T type for ATA. These interfaces made it possible to replace easily 5.25-inch disks, and to coexist flexibly with 5.25-inch disks. With the dissemination of personal computers, the SCSI model (external) and ATA model (built-in) became mainstream.
As the 1990s began, improvement in recording density was accelerated by using an MR head, and unit memory capacity increased at 100% a year. Thus, it became possible to achieve adequate capacity and performance even with 3.5-inch disks, and 5.25-inch and 8-inch disks disappeared.
|Completion date||January 1987||July 1987||December 1988|
|Number of disks||2||4||4(Metal)|
|Average Positioning time||80ms||35ms||25ms|
|Disk rotation speed||3,600rpm||3,490rpm|
|Average rotational delay||8.4ms||8.6ms|
|Data transfer speed||625Kbyte/s||938Kbyte/s||995Kbyte/s|