On Sat, 12 Jan 2008, Catalin Patulea wrote:
- I believe (correct me if I'm wrong) that, in general, power consumption is proportional to the core frequency. Let the power consumptions of the cores be P_1 = k*f_1 and P_2 = k*f_2.
An accurate estimation of power consumption in digital electronics is not so easy to figure out. However, as a rule of thumb, you may assume there's a constant power dissipation which is due to leakage (non-ideal switches allowing current to flow even where and when it should not), and a "dynamic" power dissipation that is proportional to Vdd (the switching voltage) and to _the square_ of the switching frequency. So the above would be better written as P_1 = P_{1,leak} + k * f_1^2, meaning that if you run the CPU twice as fast, you need four times the energy (ignoring leakage). That's why clock throttling helps _a lot_ in reducing battery drain!
Hope I remembered things correctly from my University classes :-) Best to everybody and thanks for your work on Rockbox! Luca -- "I have seen things you people would not believe. Attack ships on fire off the shoulder of Orion. C-beams glittering in the dark near the Tannhauser Gate. But... all those moments will be lost in time, like tears in rain." (Roy Batty, from Blade Runner, 1982) _ ASCII ribbon campaign ( ) - against HTML email X & vCards / \