History (1984): DEC TU81

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TU81
Big 9-track tape-drives for heavy backup duties

The TU81 servo/control module uses a Motorola 6802 processor, a variant of the 6800 with 128B of internal RAM and an internal clock oscillator.

There is also a 6821 Parallel Interface Adapter chip used for communication between the servo/control microprocessor and the Formatter Write microprocessor (on a different board).

Two 6840 Programmable Counter / Programmable Timer Module chips are used to count servo tachs.

The firmware is stored in two ROM chips.

Manufacturer: Digital Equipment Corporation
Media: standard half-inch tape
Tape density: 1,600bpi (PE), 6,250bpi (GCR)
Tape speed: 75 inch/s (high speed streaming mode) or 25 inch/s (start/stop mode or low-speed streaming mode)
Year introduced: 1984/1985