【Fujitsu】 FACOM 6425 and F6427 Magnetic Disk Units

The FACOM 6425A2, B4 and C4 were high-speed, high-capacity magnetic disk units from Fujitsu which were the first to achieve high-speed data transfer at 3Mbyte/s. They were completed in September 1983. These magnetic disk units achieved a high capacity of 630Mbyte by using the same 10.5-inch disks as the FACOM 6421 and increasing memory capacity by 1.4 times that of the FACOM 6421 through improvement of recording density. Recording density in the track direction was increased by 1.6 times to achieve this expansion in memory capacity, and as a result the data transfer speed became 3Mbyte/s. Previously, the maximum data transfer speed of a standard I/O interface for connecting I/O with a channel was 1.5Mbyte/s (with 1 byte width), but this was increased to 3Mbyte/s by using a Data Streaming Feature. In this way, high-speed transfer at 3Mbyte/s was achieved for the first time for all types of transfer, from the magnetic disk unit, through the magnetic disk controller and channel unit, to the main memory of the host computer.

There were 3 types of FACOM 6425: the model A4 and C4 which had 1 or 2 adapters for connection with the magnetic disk controller and 2 DEs (Disk Enclosures), and the model B4 which had no adapter.

In 1986, Fujitsu completed the FACOM 6425M4/N4 magnetic disk unit which increased memory capacity to twice that of the FACOM 6425A4/B4/C4, and in 1988 they completed the FACOM 6425HA4/HB4 which increased memory capacity by 3 times that of the FACOM 6425A4/B4/C4. To facilitate migration of data when introducing new equipment, the memory capacity of a single track in these units was set to 47,476 in all models.

In 1990 Fujitsu completed the F6427H which used a compact 8.25-inch disk. This unit reduced installation floor area to 1/3.6 and power consumption to 40% compared to previous models. This equipment achieved high-performance, high-reliability and improved cost performance in combination with the features of the newly developed disk controller. This unit achieved the world's highest capacity of 30Gbyte/unit.

Specifications of F6425,F6427 High-speed, and High-capacity Magnetic Disk Units
Model name F6425A4
Completion date September 1983 August 1986 December 1988 April 1990
Disk Memory capacity 630Mbyte 1,260Mbyte 1,890Mbyte
Disk size 10.5inch 8.25inch
Capacity/track 47,476byte
Positioning time 15ms 17ms 15ms 12ms
Rotation speed 3,600rpm 4,340rpm
Average rotational delay 8.3ms 6.91ms
Data transfer speed 3.0Mbyte/s 4.5Mbyte/s
Unit Number of installed DEs 4 4/8/12/16
Memory capacity 2.52Gbyte 5.04Gbyte 7.56Gbyte 7.56Gbyte
F6425C4:Equipped with 2-pass cross-call Standard 2-pass cross-call Standard 2-pass cross-call
Optional 4-pass cross-call
Standard 4-pass cross-call
Controller F1774C F1774C/F1700 F1700 F1700

FACOM 6425C4/B4 Magnetic Disk UnitFrom the right, the photo shows the FACOM 1774C Magnetic Disk Controller, FACOM 6425C4 and FACOM 6425B4.Disk Enclosure for FACOM 6425A4/B4/C4FACOM 6425HA4/HB4 Magnetic Disk Unit
FACOM 6427HA/HB Magnetic Disk Unit