CPU For Dummies

CPU stands for Central Processing Unit. It’s the heart or rather the brain of all the modern desktops, laptops, tablets and smartphones. What does it do? Obviously, processing information.

CPU For Dummies

Just imagine an office room full of clerks in their cubicles. Every clerk is a transistor. The whole room full of transistors is a CPU. It processes the incoming instructions the way old-time clerks processed incoming papers and handed them out for further processing or for their boss to see and evaluate the result. Right now, as I’m printing this text on my old laptop, my transistors-clerks are working, deciphering the instructions from the keyboard and turning them into letters. And other clerks are saving this very word file. The clerks are teamed to fulfill some specific parts of work and the whole load is shared among these teams called circuits.

For example, my clerks have loads of work to do. I print, I browse, I watch movies and I sometimes edit my video. The instructions are coming in as an avalanche, threatening to bury my clerks. That’s why, they have to sort the incoming data some way and set up the priorities right. Imagine, that a clerk has an “IN” and “OUT” baskets of his or her desk where to store the papers processed. These baskets are cache memory. The larger are the baskets, the easier is the work.

Are you still with me? All right, now, if an enterprise is large enough, one office room may not be enough, may it? You have to hire more clerks and lease or build more office rooms. (And if we’re talking office rooms and buildings, you shouldn’t wonder that CPU structure is called architecture.) And here where the multi-core CPUs come in. Every core is one office room with transistor-clerks in it. Modern processors can have up to 16 cores, and some server models – up to 24 cores. But the most common CPU models for PCs have no more than 8 cores.

So, we’ve learnt that every core is an “office room” in which a task is performed. Do clerks from one room cooperate with their workmates from the other one? But of course! There are two types of such cooperation. The task can be shared between the room so that it will be done faster. This process is called multithreading. But often, the work is so big, that every office room has to take more than one task. This process is called hyperthreading. Top-class and mid-class CPUs feature both, the number of threads in hyperthreading specified in their documents. Top-class CPUs are capable to process up to 4 threads per core.

Of course, the CPU has loads and loads of work as it also manages other parts of the personal computer or the portable device. It controls operative memory or RAM, hard disks or solid state drives (HDDs or SDDs), video and sound cards and input-output ports. Back to our office room metaphor, clerks have landline phones which connect them to any other department or working shop of the enterprise. This way clerks can send and get any data, instruction or report. These “landlines” are called buses. They have their own speed and topology that’s reflected in CPU specifications.

Of course, our clerks aren’t omnipotent, they can manage only so many departments. Thus, the capacity of RAM, storage type and capacity are limited by a CPU model. Equally, HD video support or multithreading depends on CPU capabilities. And this fact is mentioned in CPU specs as well.

What about clock speed? What is it and how does it effect a CPU performance? In a nutshell, the clock speed or rate defines a number of operations per second. The higher is the speed, the faster are the “clerks”. Picture the office room once again and don’t forget a large clock on the wall. The clock ticks and the clerks have to fit in. The minimal period of time needed for one operation is called clock cycle.

But processors with equal clock speed might not be equal in performance. Performance rate is the sum of many factors, CPU architecture being the crucial one. Just the way office buildings differ. It matters, if the building is modern and light, or outdated with dark rooms and winding corridors.

Of course, you can make your clerks work faster by winding up the clock on the wall. No wonder, the process of CPU boosting is called overclocking. But be careful: not every CPU is designed for overclocking and you can exhaust your ‘employees’. In other words, the CPU life can be dramatically diminished through overclocking.

One last question you may have is: why clock speed is measured in frequency units – Hz, MHz and GHz. Because CPUs talk current frequency language.

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