In May 1988, NEC announced the D5655 5-inch, high-capacity, high-speed hard disk unit for OEM.
This unit improved performance of the magnetic recording media, increased recording density by using 2-7RLL (Run Length Limited) code, which has a minimum magnetization reversal 1.5 times that of MFM (Modified Frequency Modulation), and achieved a memory capacity of 179.8MB, the highest in Japan for a 5.25-inch thin hard disk unit.
An average seek time of 18msec, the fastest in Japan, was achieved by, among other things, lightening the magnetic head movement mechanism and using a high-performance voice coil motor.
Noise during random seek was a low 45 decibels or less.
| Disk diameter(inch) | 5.25 |
|---|---|
| Number of disks | 4 |
| Number of heads | 7 |
| Number of cylinders | 1224 |
| Recording density(bpi) | 19610 |
| Track density(tpi) | 1240 |
| Recording system | 2-7RLL |
| Memory capacity (unformatted) (MB) | 179.8 |
| Average seek time(msec) | 18 |
| Average rotational delay(msec) | 8.4 |
| Data transfer speed(kB/sec) | 1250 |
| Rotation speed(rpm) | 3573 |
| Unit dimensions(mm) | 146(W)×203(D)×41(H) |
| Date first shipped | April 1988 |
