[mythtv-users] CPU power (was Possible small HD frontend)

Brian Phillips brian.phillips at gmx.net
Sat Mar 22 14:45:57 UTC 2008


Brian Wood wrote:
> So slowing the clock is just a thermal issue? The same amount of work
> over a longer time would require heat to be removed at a slower rate,
> thus allowing slower fans?  
> 
> Slowing the clock is certainly touted as "green" in a lot of circles,
> but it wouldn't surprise me if it is marketing and not engineering. I
> seriously doubt the power saved by slowing the fan(s) would be
> significant.   

The heat generation is a product of how hot the transistors are currently
(and other factors).  Slowing the clock cycle gives you more time to remove
the heat generated from the last clock cycle, so you could make one argument
for slowing the clock.  The argument would be that, keeping everything the
same, you are losing less power to heat generation per clock cycle with a
slower clock cycle because your CPU is running cooler.  On the flip side you
are running more cycles of your fan between clock cycles, and spending more
power there per clock cycle which could very well negate your power savings
due to less heat generation.

I would call it "greener", but I wouldn't call it "green".  I would equate
it with saying "My car burns ethanol, instead of straight gasoline."

I would also say the marketing department came up with the "green" idea.  In
today's Al Gore world, that's what is selling, and they know it, forget what
we engineers think! ;)

Brian Phillips



More information about the mythtv-users mailing list