Tried this morning some tweaks and something is still weird . I was thinking the n9 may be unstable due to governor that changes often frequencies and voltages so I set the scale_min_freq same like scale_max_freq , so the cpu will stay at max everytime . I also tried to set governor to performance but phone freezes immediately when I set a higher frequency than 1360mhz .

Device is acting weird when I am doing these tweaks , it's very laggy and it sets a frequency after I change the scale_min_freq . I don't know how to explain better this situation , here's an example .

current speed is 1350mhz
set scale_min to 1400mhz
echo 1400mhz 1.4v to opptimizer
conky and everything else still showing 1350mhz
set scale_min to 800mhz (phone freezes)
set scale_min to 1400mhz (phone works but very laggy)
conky and everything else showing 1400mhz now

I can repeat these steps for any frequency , I also tried for 1700mhz and it worked , conky was showing 1700mhz but I know it's just a bug .

here's also a video of how device is acting after I pass the 1360mhz with the method presented above : http://www.youtube.com/watch?v=5H_bc_IkuOQ

Fast report since I don't have currently time for proper testing;

If I use UI I can't get to 1,3GHz with default voltages, eg. when touching only the cpu speed slider, and my phone crashes.

If I just
echo 1400000000 1375000 > /proc/opptimizer
it still seems solid and I can't get my phone crashing with normal use. I used conky to check the cpu speed.

Is there a way to run the mandelbrot test from command line?

Everytime when I overclock too much and device gets laggy and iresponsive the signal drops like I have no SIM inserted .

That shouldn't be possible, anything you do in the UI is passed to the sysfs entry exactly the same as if you're typing it manually. You can't run that test without the UI to start it, it's part of it.