Processor and chipset
When purchasing any personal computer, one of the fundamental factors to consider is the central processing unit (CPU). In a notebook computer this is even more important, as the CPU is not only the brains of the machine, it is one of the factors in determining how long the notebook will operate while disconnected from the mains power and running on the battery.
The processor must be able to deliver the performance you require while not draining the battery too fast. Of course, processor vendors are not charities, and the more value they put into the CPU -- speed, power reduction, lower heat emissions for super-portable notebooks, and so on -- the higher the price tag of the processor and, correspondingly, the overall price of the notebook.
Which notebook you buy, and which processor it includes, will in most cases depend on your budget. Within the AMD and Intel mobile processor range there is a wide variety of individual CPUs.
It's important to know that just because processors are marketed under the same brand, such as Intel Centrino Duo or Turion 64, it does not mean that they are all identical. For example, processors in the same range can differ in micron technology used, the amount of Level 2 cache, clock speed and the number of CPU cores that are on the processor. Within processor brands, differences exist in the underlying silicon gate technology (eg, 65-nanometre). Generally, the smaller the build process is, the newer the technology.
Other differences include the power consumption figures, the power management technologies included, and the amount of secondary (Level 2) cache on the processor. All these factors affect CPU performance, which is why Intel and AMD have both moved away from using just the gigahertz (GHz) speed to identify a processor and instead have started using numbering systems that they feel better label their products.
Performance impacting CPU technologies
Micron technology: The size of the transistor technology on the CPU. Smaller means the processor can run more quickly and will generate less heat.
System bus/Front-side bus (FSB) speed: This is the channel through which the processor accesses the main memory. The faster this is, the more quickly information can be pulled from memory.
Secondary (Level 2) cache: Secondary cache is a small amount of memory (generally ranging from 2MB to 4MB on notebook processors) that is on the actual CPU. The memory, while small, is accessible at a very high speed and reduces the need for the processor to access the main memory, which is done via the slower system bus.
Voltage: Cutting the voltage (and therefore the speed of the processor) helps reduce power consumption as well as heat generation, which is a significant factor in cramped notebook cases.
Power management: Some technologies modify the physical power consumption of the CPU based on operational requirements. Techniques include reducing the clock speed or implementing variable voltages. This reduction of power consumption provides longer mains-free operation.
Cores: These days most notebook CPUs are at least dual-core CPUs. This means that there are effectively multiple processors on the one chip. Dual-core CPUs are not only capable of doing multiple tasks, or in some cases, splitting a single task between the cores, but also offer additional power management features. Quad-core CPUs are yet to find their way into notebooks, but it hasn't been ruled out.