Difference between revisions of "Vonada's Engineering Maxims"
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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; | + | # 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 27: | Line 27: | ||
: "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 12:36, 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
