In July 1985, NEC announced the D3116 and D3126 3.5-inch hard disk units for OEM.
These units achieved high recording density by using the first plated disk media for 3.5-inch, ensured reliability at high track densities by employing the same embedded servo system for head positioning control as the D5126 5-inch fixed disk, and achieved the highest capacity in Japan at the time for a 3.5-inch fixed disk (25MB with the D3126) in almost the same size as a 3.5-inch micro floppy disk unit.
In 1987, NEC shipped the D3126H, which improved average seek time from 85msec to 35msec by changing the magnetic head movement system from a step motor to a torque motor, and the D3146H which doubled the number of disks while keeping the same magnetic head system, and increased memory capacity to 51MB.
| Model name | D3116 | D3126 | D3126H | D3146H |
|---|---|---|---|---|
| Disk diameter(inch) | 3.5 | |||
| Number of disks | 1 | 2 | 2 | 4 |
| Number of heads | 2 | 4 | 4 | 8 |
| Number of cylinders | 615 | |||
| Recording density(bpi) | 15000 | 14000 | ||
| Track density(tpi) | 750 | 850 | ||
| Recording system | MFM | |||
| Memory capacity (unformatted)(MB) | 12.8 | 25.6 | 25.6 | 51.2 |
| Average seek time(msec) | 85 | 35 | ||
| Average rotational delay(msec) | 8.42 | 8.33 | ||
| Data transfer speed(kB/sec) | 625 | |||
| Rotation speed(rpm) | 3564 | 3600 | ||
| Unit diamensions (mm) | 101.6(W)×151(D)×40.6(H) | 101.6(W)×146(D)×41.3(H) | ||
| Date first shipped | March 1985 | September 1985 | October 1987 | June 1987 |
