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SubjectRe: [patch] recover lost ticks
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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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