[HARDWARE] Cost of crunching (was: Mac Questions)

Peter Cordes peter at llama.nslug.ns.ca
Sun Mar 17 17:29:00 EST 2002

On Wed, Mar 13, 2002 at 03:50:21PM -0700, John L. Bass wrote:
> It doesn't work to just use processor power, there are a lot of other components
> in the "system" ... even with high integration PC's which clock the front side
> buss (and everything on it) at 100/133mhz. The LCIII will not tick unless the
> processor buss and get memory cycles ... and the memory controller and DRAM's
> use power too.

 You can calculate the incremental cost of having the CPU working hard vs.
idling, assuming the computer would be left on all the time anyway.  (If
that's not the case, then the incremental cost of crunching is a lot higher.)
 On x86 CPUs, I know there is a halt instruction that stops the clock and
everything on the CPU until the next interrupt.  Most OSes for that platform
use it in their idle loop.  Win9x is a notable exception, but even without
it, running an idle loop switches a lot less transistors (and thus uses less
power) than d.net.  This being the hardware list, I don't think I need to
elaborate on why d.net uses more power than pretty much anything else you
could run.

#define X(x,y) x##y
Peter Cordes ;  e-mail: X(peter at llama.nslug. , ns.ca)

"The gods confound the man who first found out how to distinguish the hours!
 Confound him, too, who in this place set up a sundial, to cut and hack
 my day so wretchedly into small pieces!" -- Plautus, 200 BCE
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