When choosing a laptop, you must pay attention to the important specification, CPU.
CPU is the heart of a computer, and takes charge of the operating system and every application you use. A better CPU means higher running speed, but usually it also means shorter battery life and more money. AMD’s or Intel’s CPU are the most widely used in laptop.
Ultraportable PCs generally use low-voltage AMD or Intel processors. These chips are usually dual-core CPUs that are quite similar to the regular notebook CPUs found in larger laptops but operate at much lower clock speeds (1.2GHz instead of 2.1GHz, for example). Many processors are available in this group, but when you pick a laptop, you can obey a few general rules: More cache is better, and higher clock speeds are preferable but will cause a shorter battery life. AMD's CPUs are a bit slower than Intel's, but are priced to move.
Nowadys many laptops have both dual-core and quad-core CPUs at various speeds. Intel's Core i3 and Core i5 CPUs are excellent for most users,for example, HP ProBook 4530s with Intel Core i3 is pretty good; only people who truly need a quad-core CPU (for encoding video, playing games, or running engineering applications, for example) need the quad-core Core i7 processor.Although more cache and higher clock speeds are preferable, but any CPU over 2.0GHz is fast enough to handle all the basic stuff, like playing music, surfing the Web and playing Web games, displaying online video, and managing e-mail.
You'll still find many laptops on sale with Core 2 Duo CPUs, which are the previous generation of dual-core chips from Intel. Core 2 Duo CPUs are enough for most tasks--just avoid the ones with low clock speeds and small caches (1MB or 2MB), if you can. Don’t buy cheap laptops bearing Intel Celeron or Pentium CPUs, or those that carry AMD Sempron CPUs; these processors lower the price, but the performance is not desirable.
So, if you want to buy laptop, make sure that the CPU satisfies your need, neither too slow nor too fast.