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.
|FACOM 6621A||FACOM 6622K||FACOM 6622L||(reference)FACOM 628R|
|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|