【Fujitsu】 FACOM 472K Grouped Disk Pack Unit

The FACOM 472K was Fujitsu's first grouped disk pack unit, which provided 9 disk drives with a controller, and was completed in March 1970.

Fujitsu had the FACOM 462K which used IBM compatible disk packs (comprised of six 14-inch disks), but in order to achieve higher capacity and higher speed, Fujitsu developed their first grouped disk pack unit which enabled use of up to a maximum of 9 disk drives (8 drives for normal use, and 1 drive as a spare) for Fujitsu unique disk packs (each comprised of eleven 17-inch disks). There were two recording formats, fixed length and variable length. The former type was connected to the SFC (Sector File Channel) of the FACOM 230-35 mid-size general-purpose computer, and the latter was connected to the SLC (Selector Channel) of large general-purpose computers such as the FACOM 230-45S or higher models. The FACOM 472K had the following features:

1) A high-capacity memory of 29Mbytes per pack was achieved by using a disk pack comprised of eleven 17-inch disks.
2) As a subsystem, it was possible to connect a maximum of 8 normal use drives and 1 spare drive, thereby achieving a maximum memory capacity of 233Mbytes.
3) High-speed data transfer at 260Kbyte/s was achieved.
4) One or two drives could be housed in a single cabinet. Drives were the drawer type and could be slid forward and back. Disk packs could be removed, mounted, maintained and inspected independently of other drives.
5) It was possible to easily and accurately configure combinations of media and access equipment numbers by reinserting equipment number plugs (from 0 to 7) into the desired drive.

In September 1972 Fujitsu completed the FACOM 472L Grouped Disk Pack Unit which increased the memory capacity of a single pack to 58Mbyte by doubling the number of tracks, and reduced the average positioning time to 50ms by employing a linear motor as the positioner.

Specifications of FACOM 472K/LGrouped Disk Pack Unit
  (Reference) FACOM 462K/462K-1
Disk Pack Unit
Grouped Disk Pack Unit
Grouped Disk Pack Unit
Completion date August 1969 March 1970 September 1972
Memory capacity Track capa
Fixed length 256byte×10 256byte×18
Variable length Max.3,625byte Max.7,294byte
Fixed length 5.12×106byte 17.77×106byte 35.55×106byte
Variable length 7.25×106byte 29.18×106byte 58.36×106byte
Unit Number of drives 1drive 8drives+ 1spare drive
Fixed length 5.12×106byte 142.18×106byte 284.36×106byte
Variable length 7.25×106byte 233.41×106byte 466.81×106byte
Number of tracks/side 203 203 406
Number of cylinders/
203 203 203
number of disks/
number of sides
6/10 11/20 11/20
+1 side(Servo)
Disk pack diameter 356 mm(14inch) 430 mm(17inch)
Positioning system Pulse motor Linear motor
Positioning time Average 75ms
(Min. 25ms,
Max. 135ms)
Average 75ms
(Min. 30ms,
Max. 135ms)
Average 50ms
(Min. 15ms,
Max. 80ms)
Rotation speed 2,400rpm 2,000rpm 2,400rpm
Average rotational delay 12.5ms 15ms 12.5ms
Data transfer speed 156Kbyte/s 260Kbyte/s 312Kbyte/s
Main connected systems *1

*1:·FACOM 462K-1 (Fixed length type): FACOM 230-25/35
·FACOM 462K (Variable length type): FACOM 230-60

FACOM 472K Grouped Disk Pack UnitDisk pack for FACOM 472K