Micropolis hard Disk Drives, Specifications, Support, Specs, Jumpers, Manual, Images

Micropolis 1335

Hard Disk Drive


Model Capacity Size Height Interface Bus Type
Micropolis 1335 71MB 5.25" FHT ST506 MFM



Size 5-1/4 Inch
Interface ST-506/412
Interface Type
Encoding Method MFM
Formatted Capacity 71.3
Disks 5
Heads 8 (9 with alignment head)
Cylinders 1024
Sectors 17
Buffer Size N/A
Average Seek 28 msec
Single Track 6 msec
Rotation Speed/Avg. Latency 3600 rpm +/- 0.5%
Transfer Rate to / from. media 5 Mbits/sec
Transfer Rate to / from buffer N/A
Tracks Per Inch (TPI)
Bits Per Inch (BPI)
Dimensions 8.0"L x 5.75"W x 3.25"H
Weight 5.75 lbs.

Power Requirements

+12V +/-5% +5V +/-5% Power
Spin up 3.9A (max)
Read / Write 2.0A avg 0.9A avg
Typical 29 Watts


These drives actually have 9 heads, where 8 read/write heads are used for user data and the topmost head, head 9, is used for servo tracking data.

Drive Addressing and Interface Termination

Note that due to how the jumpers are located on the PCB and how the PCB is mounted inside the drive's metal chassis, jumpers are hard to reach. That's why the PCB is mounted in a way that it can be swung out. Place the drive on your workbench vertically with the PCB facing you. Then loosen the two screws located on the top. The PCB is mounted with hinges on the bottom and can then be poped down for inspection and easier access to the jumpers and motor assembly.

DS1, DS2, DS3, DS4 Drive Select Jumpers
  The Drive Select jumper locations are identified as DS1, DS2, 
  DS3, and DS4. Only one Drive Select jumper is installed on a 
  drive. The drives are shipped with the jumper installed at DS1.
  For every drive in a PC/AT installation, move the jumper from DS1
  to DS2 (the special twisted interface cable that is generally
  used takes care of assigning a unique address to each drive).
  Some other systems may require that each drive be jumpered to a
  unique address (i.e., different DS numbers).

RN1 Interface Terminator
  The Interface Terminator factory installed at RN1 provides proper
  termination for the interface lines. When daisy-chaining multiple
  1335 drives, leave the terminator in the last physical drive on
  the daisy chain cable; remove the terminator from each of the
  other drives. In most PC/AT installations, the C: drive is
  actually at the end of the cable and should retain the

W1 Write Fault Latch
  W1 is the Write Fault Latch. If W1 is present and the drive
  encounters a write fault, all writing to the drive is inhibited
  until after the drive has been de-selected. If W1 is absent,
  fault conditions are not latched. Drives are shipped with a
  jumper installed at W1; remove it for PC/AT installations.

W2 is always installed.

W7 is never installed.

W8 is always installed.


The drive uses the de-facto industry standard for MFM disk drives, the ST412 interface, which was adopted by numerous HDD manufacturers of the time and was widely used well into the 1990s. With its origin in floppy drive interfaces, this hard disk interface standard goes back to the Shugart Associates SA1000's interface, an 8-inch hard drive. The successor hard disk drive, Shugart Associates ST506, was the first 5.25 inch hard disk drive. It stored up to 5 MB after formatting (in 153 cylinders, using 4 heads, 26 sectors/track, 256 bytes/sector). This device was followed later in 1981 by the similar ST412 HDD which made 10 MB of on-line storage available by doubling effective cylinders to 306. At that point, the ST412 interface semantics had settled.

OEM Applications

The drive Micropolis 1335 was one choice for Commodore Amiga SCSI controller expansion cards used during the late 1980s and early 1990s. Such cards connected to the Zorro II Amiga bus to equip an Amiga computer system with HD storage space. One example of a card that was able to control the drive was the Kupke GOLEM HD 3000 (alternative pictures) which is an MFM capable controller.