This was a cartridge disk drive for small computers, developed in 1972 by Mitsubishi Electric. It was used as a file device for minicomputers and office computers. This disk drive was equipped with one top-loading disk cartridge (14-inch) equivalent to the IBM-5440, and one fixed disk.
The features of this unit were as follows:
- It had high-speed positioning performance more than twice that of previous Japanese-made products.
- No mechanical wear was realized by servo-detent positioning system which determined a position electrically using a combination of magnetic sensor and linear motor. (Previously, a detent system was used, where position was determined mechanically by engaging a claw into a turning gear.)
- The head pressing/holding mechanism was simplified and lightened, and access time was speeded up, by using Mitsubishi's unique self-pressing magnetic head technology.
- The disk and head were cleaned by internally circulating air produced by a high-performance air filter (99.97% 0.3μm).
- A temperature compensator (pre-heater) was available as an option, and this widened the operating temperature range from the previous 15-35°C to 5-35°C, and facilitated use in cold regions.
- It was equipped with functions such as write-disable, self-diagnosis and dual-access, and could be used in a fashion similar to large disks.
| Memory capacity | 6.4MB |
|---|---|
| Track capacity | 7,942byte |
| Recording system | FM |
| Bit density | 2,248bit/inch |
| Track density | 100track/inch |
| Disk rotation speed | 1,500rpm |
| Data transfer speed | 198.6Kbyte/s |
| Positioning time | Min. 8 ms,Max. 80ms,Average 40ms |
| Rotational delay | Average 20ms |
| External dimensions(Width x Height x Depth) | (Standalone type) 910mm×740mm×490mm (Separate power supply) 510mm×310mm×840mm |
| Weight | (Standalone type) 140kg (Separate power supply) 75kg |
In 1973, Mitsubishi Electric announced the M802, which doubled track density to 200track/inch, and achieved a memory capacity of 12.8MB.
In 1975, they announced the M802F with a more compact drive and built-in power supply.
In 1976, they announced the M803F. This model doubled its bit density to 4420bit/inch and achieved a memory capacity of 25.5MB, by converting the recording system from FD (Frequency Doubling) to MFM (Modified Frequency Modulation) in the drive.
