Assassin's Creed lag

[YRX2000]

I am a great fan of AC. I've played through almost the whole series on my Samsung Ativ Book 8, but had not issues whatsoever until I came to AC3 and AC4.
My specs are the following:
CPU: i7 3635QM
GPU: AMD Radeon HD 8870M
RAM: 8GB DDR3

Most of the time, I play games at high settings at either 1920x1080 or 1280x768. Games run fairly smoothly. Just not AC3 and AC4. This is a list of examples:
Need For Speed Most Wanted 2012: 1920x1080, high settings, runs at about 45 fps
Call of Duty MW3: 1920x1080, medium to high settings, runs at 55+ fps
GTA IV: 1920x1080, high settings, runs at locked 60 fps
Minecraft: high settings, runs locked at 60 fps
Older games like TF2, Portal 2, Borderlands, all run at 1920x1080, ultra settings locked at 60 fps.

But for AC3 and AC4, both after entering the city, (AC3: Boston; AC4:Havana), the frame rate drops drastically. On average the game runs at about 15 fps. No matter how low the resolution and settings I use, the game stays laggy. I REALLY love AC games, and I would really appreciate it if this could be solved.

This is my first time posting a question here, so I would really appreciate it if this could be solved.

Just FYI, the beta AMD drivers for my gfx card screws everything up. So upgrading driver is not an option for me.

 

[dannyboy2233]

I hate to break it to you, but those FPS are to be expected. I was watching a benchmark video earlier today (on AC4), and even with a 780Ti at 1080p, they were still only getting 55 FPS. As for the problem with AC3, I'm not entirely sure.

 

[rolandzhang3]

That's a known problem with AC3, the frame rate in Boston is woeful to say the least, and I'm sure it's the same for AC4

The latest AC games have been pretty badly optimized for the most part, I was getting similar framerates for running AC3 on high and low, both dipped to 20FPS upon entering boston

As above those framerates you get seem normal, when the best desktop GPUs out there can barely max the game and run over 60FPS, you know you've got one heck of a PC "port"