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)

They are:

1. There is no such thing as ground.
2. Digital circuits are made from analog parts.
3. Prototype designs always work.
4. Asserted timing conditions are designed first; un-asserted timing conditions are found later.
5. When all but one wire in a group of wires switch, that one will switch also.
6. When all but one gate in a module switches, that one will switch also.
7. Every little pico farad has a nano henry all its own.
8. Capacitors convert voltage glitches to current glitches (conservation of energy).
9. Interconnecting wires are probably transmission lines.
10. Synchronizing circuits may take forever to make a decision.
11. Worse-case tolerances never add - but when they do, they are found in the best customer's machine.
12. Diagnostics are highly efficient in finding solved problems.
13. Processing systems are only partially tested since it is impractical to simulate all possible machine states.
14. Murphy's Laws apply 95 percent of the time. The other 5 percent of the time is a coffee break.

(#10 is apparently a reference to meta-stability. The seeming 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.)

External links

• PDP-11/45: V6 Unix Troubleshooting, Part I Part II - a wonderful, lengthy and painful example of Maxim #12 at work