RL0x disk drive

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RL01 / RL02
Manufacturer: Digital Equipment Corporation
Drive Controller(s): RL11 (UNIBUS)
Capacity: 5.2 Mbytes (formatted) (RL01)
10.4 Mbytes (formatted) (RL02)
Transfer Rate: 512 Kbytes/sec
3.9 usec/word (peak)
Average Access Time: 67.5 msec
Revolutions Per Minute: 2400
1/2 Revolution Time: 12.5 msec
One Track Seek Time: 15 msec
Average Seek Time: 55 msec
Maximum Seek Time: 100 msec
Head Switching Time: 8 msec (maximum)
Total Surfaces: 2
Tracks Per Surface: 256 (RL01)
512 (RL02)
Sectors Per Track: 40
Words Per Sector: 128
Tracks Per Inch: 125 (RL01)
250 (RL02)
Density: 3725 bpi (maximum)
Recording Method: Modified Frequency Modulation (MFM)
Start Time: 40 seconds
Stop Time: 30 seconds
Physical Size: 19" W x 10-1/2" H x 25" L
Weight: 55 pounds
Power Consumption: 160W (running); 550 VA (starting)

An RL01 drive

The RL01 and RL02 are single platter, removable pack disk drives, introduced in 1976 and 1978 respectively, by DEC. They used an IBM 5440 type pack, as used on the IBM System/3.

The RL01 is a 5MiB drive, and the RL02 is 10MiB; the latter is a high-density version, with twice as many tracks per surface, but otherwise mostly identical.

To keep the heads properly aligned on the tracks, it used a servo system driven by servo data written on the pack (along with sector headers) at the factory. Packs cannnot be low-level re-formatted in the field, and are not compatible with both drive types.

Early versions of the drives included a set of brushes that swing out over the platter on start-up; these were deleted in later versions.

An RL02 drive

Up to 4 drives may be attached to a single controller; the drives are connected serially, with a terminator on the 'out' port of the last drive on the string.

The UNIBUS contoller is the RL11, a single hex card. The QBUS controllers are the RLV11 and RLV12; the former consists of two quad cards, and needs a QBUS backplane with CD interconnect; the latter is a single quad card, and is also the Q22 version.


An RL01 pack

4.3 BSD disktab

rb02|RB02|DEC RL02 on 730 IDC:\

Emulating the RL02

An RL02 cartridge

Reinhard Heuberger has created an open source emulator for the RL02 (and RL01) using a Terasic DE0-Nano Altera Cyclone IV FPGA board, extended with necessary interfacing hardware and an SD card slot. The emulator can be used with a real PDP-11, for example.

* Home page of project
* Picture of the simulator connected to a PDP-11/53