This is collection of all fix available for fixing Boston Lag in Assassin's Creed 3 (+ my own new fix)

No need to download any software except latest drivers :)

Every Step is Compulsory

Step I

Turn Off V-Sync by editing Assassin3.ini (Directory: C:\Users\USER\Documents\Assassin's Creed III)

Change "VSync=1" to "VSync=0" in Assassin3.ini and save it

Step II

Only for nVidia users

Open nvidia control panel

Then select "Manage 3D Settings"

Then click on "Program Settings" tab and select "ac3sp.exe" from dropdown box

Select as given below

multi-Display/mixed gpu acceleration - Single Display performance mode

Power Management mode - Prefer Maximum Performance

Threaded Optimisation - Off

Note: ATI users can try similar things in their Graphic card control panel

Step III

Run Assassins Creed 3 SP then press "Alt + Tab" now open task manager by "Ctrl + Shift + Esc "

For Windows 8: Press the Detail tab

Then Right Click "ac3sp.exe" and set priority as "Realtime" or "High"

and again right click on "ac3sp.exe" and click on "Set affinity" and tick all

For Windows  7: Right Click "ac3sp.exe" and set priority as "Realtime" or "High"

and again right click on "ac3sp.exe" and click on "Set affinity" and tick all

WARNING: Set "ac3sp.exe" priority as "Realtime" only if your cpu is quad core or more

-thanks to tzzsmk

DONE!!

I myself got fps boost of 10-15 fps.You may even get more :)

And I am playing at high settings in boston with 40fps.

My Laptop Specs:

*i7 3630QM

*GT 650m DDR3 2GB

*8 GB Ram

$$$$$$$$$$$Enjoy$$$$$$$$$$$$$