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Lecture 19 - March 17, 2003
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AGENDA:
0 Admin
1 P5 questions?
2 Ch 3.8:  
3 Quiz #4

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0 - ADMIN
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Startout Q: 

Due tonight: 
* P5

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1 - P5 QUESTIONS?
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I should have also stated that the "vspserver.cfg"
  needed to specify the "HOSTPORT".
* It does. Should have the same value as in the
  "vspclient.cfg" file.
* Choose a port > 1024 to be safe.

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2 - CH 3.8: CLOCKS IN MINIX
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What is the role of clocks in an O/S?

* time of day
* prevent processes from monopolizing CPU
* timeout functions

What is hardware like?

* simple ones tied to powerline - interrupt 50/60 Hz
* fancier uses crystal oscillator, counter, and a
  holding register

What are the modes for a programmable clock?

* one-shot mode
* square-wave mode - generates periodic interrupts

CLOCK SOFTWARE
What is role of clock driver?

* time of day
  - maintain seconds, count intermediate ticks
* CPU time quanta for processes
* CPU usage accounting
* handling ALARM system call by user procs
  - asynchronous vs. synchronous alarms
* watchdog timers for O/S
  - how different from ALARMS
* profiling, monitoring, statistics gathering


COS 421 - Lecture Notes #19		SPRING 2003	
COS421-lect-2003-03-17.doc	Page 2	Printed 17.03.03