[mythtv-users] silent and low-power: AMD or Intel?

Johnny jarpublic at gmail.com
Thu May 28 01:03:35 UTC 2009

> Please forgive me, I havent read the past discussion.  However, this
> makes no sense.
> If reducing the frequency reduces the CPU heat output, but does not
> reduce the overall power consumption, where did the energy that was
> being spent as heat go?

Generally the clock frequency doesn't have the affect on power
consumption that people assume it does (eg 1/2 clock frequency does
not equal 1/2 the power). The power is much more dependent on the cpu
voltage. Generally to get a CPU to run stably at a higher frequency it
requires a higher voltage. Likewise if you underclock a CPU you can
get it to run stably with a lower voltage. So it is the change in the
core voltage that is primarily responsible for the change in power.
Also it would probably be more enlightening if we had numbers while
the cpu is fully loaded with something like prime95 or cpuburn, and
numbers for when it is idle. I think this would tell a slightly
different story. At idle the CPU is doing minimal work and much of the
chip will be minimally used either way. Therefore it will be less
affected by clock frequency. But under full load I would think the
higher clock frequency would come into play. I am not sure about all
of this, I am sure chips are way more complex than what I learned
about in my undergrad systems architecture class many years ago.

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