Raspberry Pi B+ Overclocking: Force Turbo not working

Question

I am overclocking my raspberry pi. I have selected the turbo option from the raspi-config. I have found out however that the Pi was not running consistently at 1GHz. I have tried setting the governor (in root using echo ...) to "performance" however it reverts to the default "on demand" after reboot. I need the pi to run consistently at 1 GHz so I decided to select the force_turbo=1 at config.txt. However, it does not run consistently at the set arm frequency but runs at the default 700MHz even at 45% cpu load while running my code. I have check the temperature, cpu load, and arm_freq using vcgencmd (get_config, measure_temp, measure_clock) command.

Isn't the force turbo option suppose to disable dynamically changing clock frequencies and set the arm frequency set at config.txt consistently even at low load?

Here's my config.txt:

gpu_mem=64
start_x=1
dtparam=spi=on
dtparam=i2c1=on
dtparam=i2c1_baudrate=400000
dtparam=i2c_arm=on
dtparam=i2c_arm_baudrate=400000
force_turbo=1
arm_freq=1000
core_freq=500
sdram_freq=600
over_voltage=6

Here's my rc.local:

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

sudo echo performance > sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

exit 0

EDIT:

I have found the culprit. It was an undervoltage problem due to what supply I used. The problem was solved by using a separate supply. An indicator of an undervoltage problem is the appeareance of a multicolored square at the upper right corner of the desktop as well as the simultaneous flickering/blinking of the red power led of the pi. Undervoltage automatically disables force turbo to protect from sd card corruption.

Answer 1

Isn't the force turbo option suppose to disable dynamically changing clock frequencies and set the arm frequency set at config.txt consistently even at low load?

According to the documentation, yes. I don't have an explanation for why it would not.

I have tried setting the governor (in root using echo ...) to "performance" however it reverts to the default "on demand" after reboot.

Because the "files" in /sys (and /proc, and /dev) exist only conceptually -- they are kernel interfaces, not bytes stored on the SD card. Nothing set there persists across boot.

If you wish to set the governor at boot, on Raspbian you can do so via /etc/rc.local. You should not use sudo sh there, just echo performance > ....