What is the Watt Governor? How it works Control systems Why it is important Applications Relevance to computer systems

1. The Watt Governor and its
relevance to software systems
Matthew Skelton
contact@matthewskelton.net

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Watt Governor
• What is the Watt Governor?
• How it works
• Control systems
• Why it is important
• Applications
• Relevance to computer systems
• Q&A

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What is the Watt Governor?
• Mechanical device used
in steam engines to
regulate speed
• 1st-order negative
feedback device
• Invented around 1788 by
James Watt (Scotland)
• Etymology:
▫ “Governor/Government” and
“Cybernetics” both share a common
Greek root: κσβερνός (steersman)

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How it works
• Connected to machine
drive mechanism
• As speed increases,
weights are thrown
further outwards
• Opens/closes a throttle
valve to control input
• Goal: steady speed,
independent of load

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Control Systems
• Speed limiter – trucks
▫ As speed nears limit,
additional speed causes
additional throttle-down
• Steam engines
• Internal combustion
engines
• Power generation

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Why this is important
• Recall: steady speed,
independent of load
• Result: predictable output
• Allows planning of:
▫ Capacity
▫ Cost
▫ Delivery
• Better service from the
system

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Applications
• Not just mechanical devices
• Concept can be applied to
other self-regulating
systems
▫ Human societies, including
organisations
▫ Planetary weather
▫ Evolution of species
• Absence of governance
leads to “run-away” speeds
(and melt-down)

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Relevance to Computer Systems
• Physical application:
▫ Hardware power and cooling
• Computer software:
▫ Resource Governor – SQL Server 2008
• Service Management
• Cloud Computing
▫ Potential for much greater and more dynamic
scalability than before
• Problems have been solved before... since 1788!

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Any Questions?