Nizar Hawamdeh :
you think upgrading gain from dual core i7 to quad core one is not worth trying ?
It's not worth trying, it's impossible to do. There are no quad core processors on the BGA1168 socket.
Laptops are VERY specialized, they do not leave anything with wiggle room because of the space they have to cram all the parts into.
Here is a list of some things that can go wrong with the current proposed replacement.
1: The CPU is soldered to the motherboard, it would take a very skilled hand to properly detach, clean and reattach a new CPU. (We know this because it does not list the CPU as a part in the manual, it and the motherboard are a single package)
2: The best upgrade possible on that socket is a 20% more powerful CPU (i7-4578U), this CPU draws more power than your Current CPU and the motherboard might not support voltages high enough to run this new CPU.
3: The power supply might not be rated to provide enough wattage to the CPU
4: Your motherboard might not have the ability to support the GPU on the new CPU, as it is of a different tech generation.
5: I don't think the included CPU cooling system is capable of handling double the heat output.
Everybody in this thread who looked at the specs for your laptop agrees that it isn't a good idea, especially for a 20% performance increase. (The upgrade CPU is listed costing more than the laptop you would be putting it into)