Vonada's Engineering Maxims
Vonada's Engineering Maxims are a group of pithy observations about computer engineering compiled by Don Vonada, an engineer at DEC, and reproduced in:
- C. Gordon Bell, J. Craig Mudge, John. E. McNamara, "Computer Engineering: A DEC View of Hardware Systems Design" (Digital Press, Bedford, 1978)
- There is no such thing as ground.
- Digital circuits are made from analog parts.
- Prototype designs always work.
- Asserted timing conditions are designed first; un-asserted timing conditions are found later.
- When all but one wire in a group of wires switch, that one will switch also.
- When all but one gate in a module switches, that one will switch also.
- Every little pico farad has a nano henry all its own.
- Capacitors convert voltage glitches to current glitches (conservation of energy).
- Interconnecting wires are probably transmission lines.
- Synchronizing circuits may take forever to make a decision.
- Worse-case tolerances never add - but when they do, they are found in the best customer's machine.
- Diagnostics are highly efficient in finding solved problems.
- Processing systems are only partially tested since it is impractical to simulate all possible machine states.
- Murphy's Laws apply 95 percent of the time. The other 5 percent of the time is a coffee break.
(The typo in #11 - "Worse" - is in the original.)
Maurice Wilkes is reported to have said something like:
- "A digital circuit is like a tame animal, the analogue circuit is a wild animal. Every so often the tame animal reverts to the wild."
(See, for instance, meta-stability.)