RS64 disk drive

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Manufacturer: Digital Equipment Corporation
Drive Controller(s): RC11 (UNIBUS)
Capacity: 128KB
Transfer Rate: 125KB/sec (60 Hz), 100KB/sec (50 Hz)
Average Access Time: 16.9msec (60Hz), 20.3msec (50Hz)
Revolutions per Minute: ~1800 (60Hz), ~1400 (50Hz)
Media: 10" diameter nickel-cobalt plated surface with proprietary protective coating
Total Surfaces: 1
Tracks per Surface: 32
Sectors per Track: 64
Words per Sector: 32
Density: 1700 bpi (maximum)
Recording Method: NRZI
Physical Size: 10" (high), 19" (W, D)
Weight: 64 lbs
Power Consumption: 6A (starting), 2.2A (operating)

The RS64 is a fixed-platter fixed-head disk drive used on early PDP-11s. (No PDP-8 or other early DEC system device controller has yet been seen for it, although the look of its Service Manual dates it to just before the early -11's.) It could store up to 128KB of data in 64 byte blocks. It used 32 fixed read/write heads for data, and 6 heads to read timing/address tracks (in two duplicated sets of 3, for reliability; switch-over from one set to another was manual).

A special device had to be used to write the timing/address tracks. The drive had the ability to write-protect tracks 0-N ('N' set in switches).

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