Computers 101: CPUs

Central Processing Units or CPUs, also known simply as processors, are probably the most widely known component that we'll discuss on this list.  Due to marketing in the late 90's and early 00's, much focus has been placed on processing power in a computer.  Many people, while shopping for a computer, simply look at this aspect of a computer to help determine how fast of a computer it is.  Today, when looking at purchasing a computer, you'll see a lot of different terminology being tossed out.  Terms like gigahertz (Ghz), cores,  FSB (front side bus), HyperTransport Bus, QPI (QuickPath Interconnect), and cache.  We'll take a look at each of these and explain what they all mean but before we get too far ahead of ourselves, lets explain what a CPU actually does and take a look back at the history of the CPU. 

The CPU is basically the brain of your computer.  A CPU is sent instructions from a computer program and carries them out and is where most calculations take place.  There are two typical components that make up a processor.  They are the ALU (arithmetic logic unit), which, believe or not, performs arithmetic operations, and the control unit, which takes instructions from the memory and executes them.   I won't bore you with any further detail (send me a message if you want more) but that basically sums up what the processor does, technically.

When CPUs first arrived on the computer scene, they were specifically designed for each individual computer.  Many of these computers were designed for a single purpose and thus the processors were as well, making it very costly to build.  The cost drove to the invention of the integrated circuit and the microprocessor.  This integrated circuit allowed for a larger number of transistors to being integrated onto one chip, giving us the birth of the modern processor we have today.  As technology has advanced (again won't get into too much detail as this post is already getting long enough), the processors have become more and more powerful and smaller.  Today, processing power is increased by adding additional cores (fancy word for another processor) into one integrated circuit.  To date, the highest core processor easily available to the public for personal computer use, is the 6 core processor offered by AMD.

So now that we know a bit about CPUs, let's look at what to look for when comparing processors when shopping for a new computer.  As stated previously, the most common specification usually quoted by the sales person and understood by the customer is the clock speed of the processor, usually represented now a days in Ghz (gigahertz).  While this is an important factor there are other variables to consider while comparing processors to each other. 

We talked about cores earlier, and additional cores are another big factor in deciding which type of processor to look for.  It used to be you had one core per processor.  Now that we have multi-core processors, a lot has changed.  Multi-core processors have made it much easier to multitask and run performance draining programs by spreading out the load over the multiple cores.  Processing power of a computer is increased by adding additional cores, however, be confused in thinking that just by adding another core you double your performance.  Performance gained on each core is actually closer to 50%.   For our purposes here though, adding additional cores will increase your processing power and that is a good thing.

Another aspect to look at is the FSB (front side bus) of a CPU. When we were talking about CPUs earlier, remember learning that one of the functions of the CPU was taking instructions from the memory of the computer and executing them. The FSB is the rate at which the CPU can transmit data to and from the memory. The FSB is measure in mega transfers per second (MT/s). As you could have guessed, the higher the better. 

The term FSB is starting to go by the wayside, however.  While you'll still notice it if you are shopping at a lot of retail stores, modern day processors are doing away with the FSB in favor of faster and more advanced technologies.  The two main manufacturers of processors are AMD and Intel.  (We'll have a posted dedicated to both companies down the road but for the purposes of this article we'll stop there)  AMD's newest technology taking the place of the FSB is called Hyper Transport Bus, while Intel's decided on QuickPath Interconnect.  Basically, what each of these accomplish, is increasing the bandwith between the CPU and memory, speeding up drasitcally how quickly they talk to each other.  Previously with old FSB, there was one channel for information to pass on.  With these new technologies, to steal a phrase from Intel, it's like, "upgrading from an old backroad to a new freeway."  The CPU can now read and write information at the same time and is not limited by the amount of bandwith available.  Again this is a very brief summary of what this newer technology does.  If you would like it explained in more detail about what this means for a CPU and computers in general, feel free to message me.

Lastly, lets take a look at cache (pronounced like cash, stupid E...).  The other task of the CPU was processing data from computer programs.  Cache is actually cache memory and the higher the better here as well.  Cache speeding up the CPU by taking the instructions from the computer program and giving it to the CPU.  Cache is a smaller and faster version of your computer memory and stores the most used operations for the CPU to access most quickly.  There are usually multiple levels of cache.  Level 1 through level 3.  The first level is usually the smallest amount but the fastest.  Levels 2 through 3 act as a spill over for the CPU.  If the cache memory in level 1 is used up, the operations and tasks will spill over to the larger and slightly slower cache memory. 

We've touched on some of the key highlights of CPUs here.  Let's recap.  We all now know that the clock speed (the Ghz) that we all know and love, isn't the only thing to look at when shopping for CPUs.  We must also look at the number of cores on a processor, the FSB speed, and the amount of cache a CPU has.   Each of these are important when deciding what to look for in a CPU.  Take this information with you the next time your are computer shopping and wow the salesman! 

If you want to discuss any additional details of this post feel free to send me a message and we can chat.  Check back next week when we discuss our next component of a PC...the Motherboard!