【Fujitsu】 FACOM 6621A High Speed Drum Unit

The FACOM 6621A was a magnetic drum unit from Fujitsu which achieved high-capacity and high-speed transfer. It was completed in 1971. The FACOM 6622K and L magnetic drum units employed the same magnetic drum as this unit, and were also completed at this time. The 6621A employed a 4-bit parallel data transfer system, and achieved high-speed transfer of 1.2Mbyte/s-approximately 4 times that of the FACOM 6622K/L.

The FACOM 6621A and FACOM 6622L achieved an increased capacity of 6Mbyte by increasing the number of tracks and improving recording density. Increasing the number of tracks (magnetic heads) increases the total length of the drum rotor and the size of the unit, but the drum rotor was reduced in size by developing a new magnetic head which halved the previous track pitch.

Specifications of FACOM 6621 and 6622 Magnetic Drum Units
  FACOM 6621A FACOM 6622K FACOM 6622L (reference)FACOM 628R
Completion date 1971 1969
Memory capacity(byte) 6,000,128 3,072,000 6,144,000 1,048,576
Average access time 10ms 10ms(50Hz)/
Data transfer speed 1,200 KB/s 312 KB/s 225 KB/s(50Hz)/269KB/s(60Hz)
Drum Number of tracks 1,024 512 1,024 256
Rotation speed 3,000 rpm 3,000 rpm(50Hz)/3,600 rpm(60Hz)
Rotor dimensions 250ø×420 mm 250ø×220 mm
Track pitch 0.3 mm 0.6 mm
Main connected systems FACOM 230-45S/55, FACOM 230-60, FACOM 230-75 FACOM 230-25/35

FACOM 6621A High-Speed Magnetic Drum Unit