Vonada's Engineering Maxims: Difference between revisions
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'''Vonada's Engineering Maxims''' are a group of pithy observations about computer engineering compiled by Don Vonada, an engineer at [[DEC]], and reproduced in: | '''Vonada's Engineering Maxims''' are a group of pithy observations about computer engineering compiled by Don Vonada, an engineer at [[Digital Equipment Corporation|DEC]], and reproduced in: | ||
* C. Gordon Bell, J. Craig Mudge, John. E. McNamara, "''Computer Engineering''" | * C. Gordon Bell, J. Craig Mudge, John. E. McNamara, "''Computer Engineering: A DEC View of Hardware Systems Design''" (Digital Press, Bedford, 1978) | ||
They are: | They are: | ||
# There is no such thing as ground. | # There is no such thing as [[ground]]. | ||
# Digital | # [[Digital]] [[circuit]]s are made from [[analog]] parts. | ||
# Prototype designs always work. | # Prototype designs always work. | ||
# Asserted timing conditions are designed first; un-asserted timing conditions are found later. | # 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 [[conductor|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. | ||
# Every little pico farad has a nano henry all its own. | # Every little pico farad has a nano henry all its own. | ||
# | # [[Capacitor]]s convert [[voltage]] glitches to [[current]] glitches (conservation of energy). | ||
# Interconnecting wires are probably transmission | # Interconnecting wires are probably [[transmission line]]s. | ||
# Synchronizing circuits may take forever to make a decision. | # [[Synchronizer|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. | # Worse-case tolerances never add - but when they do, they are found in the best customer's machine. | ||
# | # [[Diagnostic]]s are highly efficient in finding solved problems. | ||
# Processing systems are only partially tested since it is impractical to simulate all possible machine states. | # 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. | # 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.) | (#10 is apparently a reference to [[meta-stability]]. The seeming typo in #11 - "Worse" - is in the original.) | ||
==Related observations== | ==Related observations== | ||
| Line 28: | Line 28: | ||
: "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." | ||
==External links== | |||
* [https://fritzm.github.io/unix-v6-trouble-1.html PDP-11/45: V6 Unix Troubleshooting, Part I] [https://fritzm.github.io/unix-v6-trouble-2.html Part II] - a wonderful, lengthy and painful example of Maxim #12 at work | |||
[[Category: Basics]] | |||
Latest revision as of 10:36, 3 December 2023
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:
- 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.
(#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."
External links
- PDP-11/45: V6 Unix Troubleshooting, Part I Part II - a wonderful, lengthy and painful example of Maxim #12 at work
