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The Watt Governor and its relevance to software systems
1. The Watt Governor and its
relevance to software systems
Matthew Skelton
contact@matthewskelton.net
2. 2
Watt Governor
• What is the Watt Governor?
• How it works
• Control systems
• Why it is important
• Applications
• Relevance to computer systems
• Q&A
3. 3
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)
4. 4
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
5. 5
Control Systems
• Speed limiter – trucks
▫ As speed nears limit,
additional speed causes
additional throttle-down
• Steam engines
• Internal combustion
engines
• Power generation
6. 6
Why this is important
• Recall: steady speed,
independent of load
• Result: predictable output
• Allows planning of:
▫ Capacity
▫ Cost
▫ Delivery
• Better service from the
system
7. 7
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)
8. 8
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!