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.
| 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 | ||
