What is a CPU?
A CPU, or central processing unit, is the main processor or "Brain" of a computer. This is one of the primary determining factors of how fast a computer can operate. Other features of current CPUs are Hyper-Threading for additional virtual cores, AES, virtualization techniques or instruction set extensions like SSE and AVX.
How do I know which is the best CPU or Processor for me?
Choosing the right processor for your system can be simplified by asking what you want or need from your system.
From AMD there are a few lines to choose from: Sempron, Phenom II Athlon, Athlon II, FX, and A-series Processors. Among these are what AMD calls their APUs (Accelerated Processing Units), which are CPUs that include integrated Radeon graphics processors. AMD specializes in creating low-cost, multi-core processors for gaming and performance level systems, but they also have entry-level and mid-range processors that are great for those looking to build an HTPC or workstation on a smaller budget.
Intel is widely considered to be the industry standard when it comes to computer processing technologies. From the blistering speed of the Core i7, Core i5, and Core i3 CPUs, to the high performance of the budget-minded Pentium and Celeron processors, there is an Intel CPU solution for practically any build. Starting with the 4th Generation Intel Core I Processors, Intel integrated Iris Graphics processors into their CPUs to deliver rendering results on par with many current discrete GPUs. Intel HD graphics also provides higher 3D and 2D rendering performance, and is integrated into many Core I, Pentium and Celeron CPUs.
What are some things to keep in mind when purchasing a Processor?
There are a few important details to keep in mind when purchasing a CPU. The two most obvious are number of cores and clock speed, but equally important to installing it into your motherboard and having it work with your hardware are the socket type, instruction set, and whether or not it has integrated graphics processing, which may or may not create the need for purchasing more hardware than is really necessary.
For number of cores and core clock speed(expressed in hertz; Ghz, expressly), the number of cores is a bit more important. Intel and AMD both have many processors that feature anywhere from two to eight cores, but along with the number of cores, the core clock speed is a reasonable tell of the performance of the processor. There are many more factors, though minimal comparatively, that we can't go into now that also affect performance, but these are the two most basic features to pay attention to. Also note that the more current the processor, the better the performance as well, in general.
The other details that don't necessarily have as much to do with performance as they do functionality, are the socket type, of which each processor is strictly compatible with only one, instruction set, whether 32-bit or 64-bit, and integrated graphics.
There are several socket types for both Intel and AMD processors, and each socket type is compatible with differing types of processors.
Intel uses the following sockets: LGA 111, LGA 1150, LGA 1155, LGA 2011, LGA 2011-v3.
AMD's sockets are as follows: AM2/AM2+, AM3/AM3+, FM1/FM1+, FM2/FM2+. AMD also has what they call their AM1 platform, but is often referred to as Socket AM1 as well.
Whether a CPU is 32-bit or 64-bit will determine certain software capabilities and other specific functions, but possibly the largest difference it makes is it's memory support. Simply put, a 32-bit processor is capped at 4GB RAM, and a 64-bit processor is practically able to support as much as the motherboard will possibly allow. There are a lot more factors involved, but theoretically (READ: only theoretically) a x86 64-bit processor should be able to handle somwhere around 16.8 million terabytes of RAM. That said, for a standard consumer level PC, you can easily get by with 4GB of RAM.
Integrataed GPUs provide processors extra cores specifically used to render 2D and 3D graphics, leaving more basic processes to the standard CPU cores, thus improving overall performance and removing the requirement for purchasing a discrete graphics card. With Intel's Iris, Iris Pro, or HD Graphics, or with AMD's integrated Radeon Graphics, you'll get levels of performance ranging from HD video, up to entry and even mid-range gaming levels.
What are processor cores?
Processors were originally all single-core devices. But over time it became apparent that a good way to boost performance was to integrate multiples of these processors into the same unit so all the standard CPUs these days are multi-core (such as dual-core which has two cores, quad-core which has 4, etc.) Currently most budget or beginning-level CPUs are in the dual-core class while most performance and gamer level processors start at four cores and go up from there. While six and eight core CPUs are fairly common these days, it's logical to see that in future generations processors will naturally integrate even more cores onto the same CPU as this is a great way to boost the performance of software designed to utilize it.
What is the processor clock rate?
The processor clock rate or speed is the frequency that each core operates at. For example, if you have a Quad Core 2.6GHz CPU, that means you have 4 cores that operate at 2.6GHz each. Processor clock rates are generally measured in MHz and this is an important measurement that makes comparing different CPUs easier. Clock rates range generally from 1GHz to 5GHz currently and we can expect this range to expand in the future as technology improves and processors become more efficient.
Should I buy a 32-bit or 64-bit Processor?
The current standard for processors are 64-bit. The reason for this is that 64-bit operating systems have become the norm. It's important to stick to 64-bit unless you have a compelling reason to use 32-bit (the main reason being if you have certain software or applications that only work on 32-bit). One of the main reasons for this is 32-bit CPUs can only address memory up to nearly 4GB. In order to use more memory you will need a 64-bit processor and a 64-bit operating system.