Messages in this thread | | | Subject | Re: [patch] recover lost ticks | Date | Mon, 15 Mar 1999 22:42:13 +0100 (MET) | From | (Rogier Wolff) |
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H. Peter Anvin wrote: > Followup to: <Pine.SOL.3.96.990315104843.4272B-100000@gauguin.ececs.uc.edu> > By author: Rafael Reilova <rreilova@ECECS.UC.EDU> > In newsgroup: linux.dev.kernel > > > > 1) On Cyrix/IBM/Centaur the TSC will stop if Suspend-on-Halt is > > enabled and a HLT is executed. This is usually a very good > > thing since power comsuption goes down dramatically, but > > the time code has to compensate (and does since somewhere in > > 2.1.12x). > > > > This is just bad TSC design. There is nothing good about it.
The thing to realize is that you're shutting down a 5M transistor chip. When it's going full blast, expect say 1M of the transistors to be "working". Running just a 64bit counter is keeping just a few hundred transistors. Consider 10 bit-sections of the counter "active". The rest accounts for less than a thousandth. Say 14 transistors per counter-section, so 140 transistors are active. So the counter is just using about 1 6000th of the power of the whole chip. So, indeed there is about a milliamp to win by turning it off, but that is neglegible to what the rest of the system is using.
(At the electrical outlet, I measured a system: 55W when active, 40W when CPU idle. So the CPU (Celeron-300) draws close to 12W (+/- 80% efficiency in the powersupply), So shutting down the TSC would've cut down another 2mw from the 40 that keeps the rest of the computer spinning)
Regards,
Roger.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* * Never blow in a cat's ear because if you do, usually after three or * * four times, they will bite your lips! And they don't let go for at * * least a minute. -- Lisa Coburn, age 9
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