Shogun 2 only uses 1 core!

[ForVictory]

I have a gamer notebook with I5 4340m, 860m, W7 and 8Gb. I can play all recent games above 30+ fps, except this one.
Been playing Shogun 2 for a while and everything was smooth until I had my first big battle of around 5000 men. The FPS would be around 10. I lowered my resolution to 1024x768 and all the settings to low and I get a increase of only 8 fps, and the game looked horrible that way!
Then I noticed out of 4 cores only 1 of them was 100% while the other 3 would be around 20% and my GPU around 50%.
It is just ridiculous that a multi company like this that makes the Total Wars series PC exclusive, has been unable to optimize it well.
I can play Battlefield 4 and Far Cry 3 with everything on high at 1080 smoothly, that is because all my 4 cores and GPU are being fully used by them.
Does anyone know a magical fix for this? Perhaps W8 might be better? I sincerely doubt replacing my I5 with an I7 would matter.

[Bran Mac Born]

Go into your Shogun 2 Preferences script file located in Drive C;Users/user name/AppData/Roaming/Roaming/The Creative Assembly/Shogun 2/scripts/preferences.script.
scroll down to the bottom of the script and find these two lines:
multithreaded_model_enabled false; # multithreaded_model_enabled <true|false>, Run the battle model on a separate thread #
number_of_threads 0; # number_of_threads <int>, Set the number of threads <= 0 - automatic, >0 = explicit number #
Change it to read this:
multithreaded_model_enabled true; # multithreaded_model_enabled <true|false>, Run the battle model on a separate thread #
number_of_threads 2; # number_of_threads <int>, Set the number of threads <= 0 - automatic, >0 = explicit number #
(If you use a quad core processor the number of thread should put is 4. Click save.)
Go back to the preferences file and right click on it and go to properties and click 'read only' and then apply then ok.

[ForVictory]

Well now the one core that did the most work now works slightly more to 100% (used to be around 90%) but the other cores are still kinda lazy. So still a small improvement in a couple frame rates.