Difference between revisions of "Vonada's Engineering Maxims"
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# Digital circuits are made from analog parts. | # Digital circuits are made from analog parts. | ||
# Prototype designs always work. | # Prototype designs always work. | ||
| − | # Asserted timing conditions are designed first; | + | # 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 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. | # When all but one gate in a module switches, that one will switch also. | ||
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: "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." | : "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." | ||
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| + | (See, for instance, [[meta-stability]].) | ||
Revision as of 21:24, 5 October 2017
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"
They are:
- 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.)
Related observations
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.)
