I can't say - if energy consumption in your N900 at 500MHz is less than 4 times of energy consumption at 125MHz then it may be advantage to stick to 500MHz only. 4times - because at 500MHz CPU cycle is 4 times shorter and any energy dissipation less than 4 times of 125MHz can be a battery saver. Why in your case - I don't know your energy consumption. You can load bq27x00_battery.ko driver ("modprobe bq27x00_battery.ko"), open a second X-Term window, run a simple set of commands: while true do true done and look into values back in first X_Term window by cat /sys/class/power_supply/bq27200-0/current_now cat /sys/class/power_supply/bq27200-0/voltage_now cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq cat /sys/power/vdd1_opp cat /sys/power/vdd2_opp Try it with 500MHz and limit your N900 by 125MHz only (into scaling_max_freq) and see the values. It would be very interesting (that voltage do you use for each frequency too?)
@ 125 MHz | @ 250MHz Run #1 Run#2 | Run #1 Run#2 737 737 | 824 824 4113 4113 | 4094 4094 124800 124800 | 249600 249600 2 2 | 3 3 3 3 | 3 3 ---------------------------------- @ 500MHz | @ 850 MHz Run #1 Run#2 | Run #1 Run#2 1051 1051 | 1623 1623 4105 4105 | 4089 4086 500000 500000 | 849920 849920 4 4 | 10 10 3 3 | 3 3