Alternative Implementations for Parrot Box

R. Pasco — October 17, 1980

I. Generalized interface, stand-alone device.

A. Advantages

Portable to other machines (Apple, D0, ...).

Can be used with lightweight ‘‘hobby’’ machines to facilitate shipping to conferences and setting up demonstrations.

Lifetime within PARC transcends transition from Altos to D-machines.

Potential for expanding user community beyond Xerox/Alto world.

Interface hardware and software can be made upward-compatible with future features incompatible with Auburn (e.g. stereo).

Complements LSI group’s wafer-scale & ethernet activities.

B. Disadvantages

Requires D/A converter, sample/hold, clock, controller, interface.

II. Auburn add-on.

A. Advantages

Potentially simpler circuit takes advantage of existing D/A converter, clock, audio circuitry, interface, controller.

Can mount on existing circuit board; doesn’t need cabinet.

B. Disadvantages

Requires user to have an Auburn, and cost of Auburn with all its features exceeds cost of specialized parts in Parrot.

Requires user to have an Alto, thus limiting user community.

24 bits/timeslot * 22 timeslots * 16 kHz sample rate = 8.448 mHz clock.