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The dynamic tick patch

The dynamic tick patch

Posted Jun 9, 2005 15:53 UTC (Thu) by jg (subscriber, #17537)
Parent article: The dynamic tick patch

It turns out to take a lot of power to power up a CPU chip. It is much more than just the raw number of instructions that might execute.

So taking a 1000hz clock interrupt actually consumes a significant amount of power.

I don't know what the stats are for x86 in this area is though.

As an aside, other things take lots more power than you might naively expect. On StrongARM's of, say 3 years ago, the cost of a miss in cache to reference main memory was equivalent to executing of order a hundred
instructions in cache.


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The dynamic tick patch

Posted Jun 16, 2005 9:33 UTC (Thu) by farnz (subscriber, #17727) [Link]

Also, most CPUs take a long time to switch from run to sleep; at 1kHz tick, there's a good chance that the "sleeping" CPU is actually running for a decent stretch of time. As they can switch back almost instantly, a good power saving technique is to try and maximise the time between a "go to sleep" command, and the next wakeup, which is exactly what dynamic ticks does.


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