In April 1966, NEC announced the high-speed, high-capacity N271A magnetic drum unit, together with their announcement of an order for the NEAC Series 2200 Model 500. The unit was delivered to Osaka University in October.
To increase recording density, this magnetic drum unit used Ni-Co alloy plating for the magnetic recording surface, the dynamic pressure float tracking system for the magnetic head, and FM as the recording system.
Due to the floating system, spacing between the magnetic head and recording surface was improved from the previous 25-30μm to 6-10μm, and this contributed to raising the recording density by a few times. After the drum rotation speed reached steady rotation, a timer automatically brought the magnetic head close and floated it.
The self-clocking FM (Frequency Modulation) recording system was used to cope with the floating head and the increase in variation of the playback waveform due to temperature variation and other factors.
The drum section had dimensions of 60cm × 60cm × 82cm (height), and its volume was approximately 1/5 that of the previous drum which had a fixed magnetic head and the same capacity.
This unit was connected to and used with models in the NEAC Series 2200.
|Rotation speed(rpm, at AC60Hz)||3,540|
|Average access time(msec, at AC60Hz)||8.4|
|Information transfer speed(char/s, at AC60Hz)||76.8k|
|Number of information tracks||256|
|Memory capacity in 1 circle(bit)||12,000|
|Total memory capacity(bit)||3,100,000|
|Working temperature/humidity conditions||5-35°C,40-80%|