【Fujitsu】 M2225 Magnetic Disk Unit

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.

5.25-inch Disk Unit, Specifications of Main Models
Model name M2225AD/SA
Completion date January 1987 July 1987 December 1988
Memory capacity/unit 25.62Mbyte 76.86Mbyte 180.3Mbyte
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
Connection interface SA:SASI,AD:ST506/ST412,DR:ST506GR,S:SCSI,T:ATA
  • Developed by Nippon Peripherals, and mass produced by Fujitsu.
  • Built-in SASI controller
  • Increased media to 4 disks
  • Used 2by7 code modulation
  • Used rotary encoder motor for head drive
  • Sputtered
  • Sector servo
  • Used 1by7 code modulation
  • Used rotary VCM(Voice Coil Motor)
  • Built-in SCSI/AT controller

M2225 Magnetic Disk UnitM2225 Magnetic Disk UnitThe disk plate and head are visible. Photo of unit displayed at Yamagata Fujitsu.Various magnetic disk units, ranging from 10.5-inch to 3.5-inchFrom the left, the photo shows various magnetic disk units: the 3.5-inch M2227 (PicoBird-2, 76.86MB), 5.25-inch M2245 (Humming-4, 389MB), 8-inch (Swallow-4, 690MB) and 10.5-inch FACOM6425 DE (1.89GB). The M2227 had 1/44 the volume and 1/36 the weight of the FACOM6425 DE.