【Fujitsu】 FACOM 624 Magnetic Drum Unit

The FACOM 624A and FACOM 627A were magnetic drum units from Fujitsu. They were the first to use floating magnetic heads, and were completed in 1968.

At the time, a magnetic drum with a memory capacity of at least 10 million bits was required for purposes such as real-time data processing. However, with the previous fixed head magnetic drums, it was difficult to improve recording density to meet this requirement. Without improvement of technology to meet this requirement the drum size would have become extremely large. Thus, the FACOM 624B and FACOM 627A increased capacity by improving recording density, and this was achieved by using floating magnetic head and changing magnetic recording material.

Specifications of FACOM 624 and 627 Magnetic Drum Units
  FACOM 624B FACOM 627A
Completion date 1968
Head type Floating
Memory capacity 2,097,152byte 524,288byte
Average access time 20ms(50Hz)
17ms(60Hz)
10ms(50Hz)
8.4ms(60Hz)
Data transfer speed 120KB/s 150KB/s
Drum Number of tracks 512 256
Rotation speed 1,500rpm(50Hz)
1,800rpm(60Hz)
3,000rpm(50Hz)
3,600rpm(60Hz)
Rotor dimensions 400ø×350 mm 250ø×200 mm
Recording density 30bit/mm
Main connected systems FACOM 230-20/ 30, FACOM 230-50

  
FACOM 624B Magnetic Drum Unit