【Fujitsu】 M2301 Magnetic Disk Unit

The M2301 magnetic disk unit was the first magnetic disk unit from Fujitsu to use 8-inch, small diameter media. It was completed in June 1979. Fujitsu's 8-inch disk units were called the Swallow Series, and starting with the second generation Swallow-2 in 1981, Fujitsu moved in earnest into the OEM market for 8-inch disks. The later Swallow Series maintained its original physical dimensions, but continued to increase its memory capacity, roughly doubling every two years. The Swallow-6 (completed in 1989) had a 2Gbyte memory capacity—24 times the 84MB of the Swallow-2, which was completed in 1981. Fujitsu lead the 8-inch disk market with the Swallow Series, and the external dimensions and mounting dimensions of the Swallow disk became the international standard.

The aforementioned increase in memory capacity was achieved using the following technologies:

1) Recording density was improved by using state-of-the-art access head and disk media technology.
2) Track density was improved by using an advanced actuator structure to control off-tracking. (Swallow-2 and later)
3) High reliability was achieved by raising airtightness with a disk enclosure structure. (Swallow-2 and later)

As 5.25-inch disk units improved in performance and capacity, the market for 8-inch disk units shrunk, and Fujitsu's final product for OEM was the M2671P (Swallow-7) completed in 1991.

8-inch Disk Unit, Specifications of Main Models
Model name M2301/02
Completion date June 1979 April 1981 November 1983
Memory capacity
10/20 84 168
Disk Size 8.0inch
Number 4 6
Average positioning time 70ms 20ms
Disk rotation speed 2,964rpm 3,600rpm
Average rotational delay 10.1ms 8.3ms
Data transfer speed 1.229Mbyte/s
Connection interface SMD
  • Fujitsu's first8-inch disk,and first product for OEM
  • VCM
  • Used diecast struct

Model name M2333
Completion date November 1984 June 1987 April 1989
Memory capacity
337 690 2,027
Disk Size 8.25inch
Number 6 8 12
Average Positioning time 20ms 16ms 12ms
Disk rotation speed 3,600rpm
Average rotational delay 8.3ms
Data transfer speed 2.458Mbyte/s 3.0Mbyte/s
Connection interface SMD SMD
Notes -
  • Improved vibration and impact resistance by using a monocoque structure
  • SCSI support
  • High-density recording using a thin-film head

*1: Using M1053 controller

M2301/2 Magnetic Disk UnitFujitsu’s first 8-inch disk, the Swallow-1. Capacity was 10/20Mbytes.M2301/2 Magnetic Disk UnitPhoto viewing Swallow-1 from the top.M2322K Magnetic Disk UnitAppearance of Swallow-2.5, which had a recording capacity of 168Mbyte.
M2322K Magnetic Disk UnitPrinted circuit board installed on top of Swallow-2.5M1053A IDC (Integrated Disk Controller)A single-board magnetic disk controller. SCSI support was provided by mounting this on top of the disk.