【Fujitsu】 M2351 Magnetic Disk Unit

In 1981, Fujitsu entered the OEM market for 10.5-inch disks with a product (called the Eagle Series) based on the FACOM 6421 Magnetic Disk Unit (completed in 1981) which was the first in the world to use 10.5-inch media. The M2351A (Eagle-1), with a memory capacity of 474.2Mbyte, was completed as the Series' first product in March 1982. At the time, the industry standard disk size was 14-inches, but with the Eagle Series, Fujitsu led its competitors in using small diameter 10.5-inch media and adopting the new concept of a disk enclosure structure. With this Series, Fujitsu built an excellent position in the OEM market for high-performance, high-capacity magnetic disks.

In April 1985, Fujitsu completed the Eagle-1.5 (M2361A) which increased capacity to 689.8Mbytes. Later, Fujitsu developed the M2350 and M2360 parallel transfer magnetic disk units which enabled simultaneous recording and playback of 4 or 5 channels, and these gained popularity as external memory devices for super computers, and for use in image processing.

However, as 8-inch magnetic disks improved in capacity and performance, 10.5-inch disks were replaced later in the OEM market by 8-inch disks.

10.5-inch Magnetic Disk Units for OEM, Specifications of Main Models
  M2351A(Eagle-1) M2361A(Eagle-1.5)
Completion date March 1982 April 1985
Memory capacity 474.2Mbyte 689.8Mbyte
Positioning time 18ms
Rotation speed 4,000rpm
Average rotational delay 7.5ms
Data transfer speed 1.859Mbyte/s 2.701Mbyte/s
Mounting type 19-inch track mount
Connection interface SMD

M2351A Magnetic Disk UnitDisk Enclosure for M2351A