Triple modular redundancy
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In computing, triple modular redundancy (TMR) is a fault tolerant form of N-modular redundancy, in which three systems perform a process and that result is processed by a voting system to produce a single output. If any one of the three systems fails, the other two systems can correct and mask the fault. If the voter fails then the complete system will fail. However, in a good TMR system the voter is much more reliable than the other TMR components. Alternatively, if there is another stage of TMR logic following the current one, then three voters can be used - one for each copy of the next stage of logic.
The TMR concept can be applied to many forms of redundancy, such as software redundancy in the form of N-version programming.
Some ECC memory uses triple modular redundancy hardware (rather than the more common Hamming code), because triple modular redundancy hardware is faster than Hamming error correction hardware.[citation needed] [1]
Satellite systems often use TMR[2] [3] [4] [5], although satellite RAM usually uses Hamming error correction[6].
[edit] triple modular redundancy in popular culture
- the three pre-cogs in Minority Report lead to a conviction, even when one is in the minority.
- The separation of powers between three branches of government can correct errors committed by one branch.
- voting can be seen as applying N-modular redundancy to come to a correct choice, even though some individual humans make incorrect choices.
- To rule out that a single win was "a fluke", some competitions use a two out of three falls match.
- a ship must have three chronometers[citation needed]
- "What I tell you three times is true." -- Lewis Carroll
