[HTC Sensation] mat9v:
Forcing cpu1 online sure costs battery (about 25mA) but "mpdecision" works strangely and sometimes does not turn it on even when it is required (and not only in benchmarks, in legitimate games and programs too). With a good script you can force it on/off depending on wakestate of your phone and not depend on mpdecision.

#!/system/bin/sh
# ==============================
# Modified Dual-core CPU script
# ==============================
(while [ 1 ]

do
AWAKE=`cat /sys/power/wait_for_fb_wake`
if [ "$AWAKE" = "awake" ]
then

chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo "ondemand" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
echo "1512000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
echo "192000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

chmod 644 /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
chmod 444 /sys/devices/system/cpu/cpu1/online

chmod 666 /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo "ondemand" > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
chmod 444 /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
chmod 666 /sys/devices/system/cpu/cpu1/cpufreq/scaling_max_freq
echo "1512000" > /sys/devices/system/cpu/cpu1/cpufreq/scaling_max_freq
chmod 444 /sys/devices/system/cpu/cpu1/cpufreq/scaling_max_freq
chmod 666 /sys/devices/system/cpu/cpu1/cpufreq/scaling_min_freq
echo "192000" > /sys/devices/system/cpu/cpu1/cpufreq/scaling_min_freq
chmod 444 /sys/devices/system/cpu/cpu1/cpufreq/scaling_min_freq

chmod 666 /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
chmod 666 /sys/devices/system/cpu/cpufreq/ondemand/powersave_bias
echo "40000" > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
echo "2" > /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor
echo "15" > /sys/devices/system/cpu/cpufreq/ondemand/down_differential
echo "70" > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
echo "45" > /sys/devices/system/cpu/cpufreq/ondemand/powersave_bias
chmod 444 /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
chmod 444 /sys/devices/system/cpu/cpufreq/ondemand/powersave_bias

fi

SLEEPING=`cat /sys/power/wait_for_fb_sleep`
if [ "$SLEEPING" = "sleeping" ]
then

chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo "conservative" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
echo "384000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
chmod 666 /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
echo "192000" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
chmod 444 /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

chmod 644 /sys/devices/system/cpu/cpu1/online
echo 0 > /sys/devices/system/cpu/cpu1/online
chmod 444 /sys/devices/system/cpu/cpu1/online

fi
done &)

On that framework anyone can fine tune various settings and after placing in /etc/init.d as for example 97force can be used @ boot time easily. So create the file, place it where it belongs, reneme /system/bin/mpdecision file to mpdecision_temp and reboot the phone. True, you will lose about 25mA while awake (cpu1 is turned off while sleeping) but the system is much smoother that way and no strange performance issues in games because cpu1 did not turn on (no strange stuttering). For comparison, sitting idle and staring @ desktop with no animated background and only clock widget @ minimal brightness and only one core working is using 80-100mA, scrolling a webpage (text only - book for example) uses 250mA, I tested it by scrolling 300000+ words story on fanfiction.net (took me 5 minutes to do so), loading data from net (be it 3G or wifi) uses 400+mA (again tested by downloading a movie from my home ftp) and finally talking on 3G nets over 300mA. In most cases, like browsing net or downloading data or playing games the cpu1 will be enabled anyway by mpdecision so no loss here. The only place I am losing power is when sitting idle or reading an ebook but personally I can live with it, screen brightness @50% uses over 250mA so 25mA is an acceptable compromise.