We know that a processor must be connected to a motherboard, that many modern models require additional active cooling, and that a higher frequency doesn't necessarily mean more performance... but how does a CPU work really? A good alternative to drowning in an engineering book is a video that lasts just over twenty minutes.
Some things are taken for granted these days. A great example is turning on the computer and expecting it to work. Those of us who have had closer contact with hardware know there are... exceptions to that rule. But beyond any specific issue, we almost never stop to think about how each of its components works. Some time ago we explored hard drives and how they work. On their own, hard drives are a chilling piece of engineering, but if there is something that surpasses them, it is the CPU.
The CPU Used for the Lesson
The video you are about to see uses as an example a MOS Technology 6502 CPU, a classic that served as the brain for the Commodore 64 (using the 6510 variant) and the NES (Ricoh 2A03), among others. In the simulation, the internal clock that maintains synchronization changes about twice per second. Generally, the 6502 has a frequency of 1 MHz.
We know that "Hertz" are "cycles" per second, and "mega" corresponds to "million", so in this old CPU from the mid-70s, the clock changes its state a million times per second. Compare that to modern processors with frequencies comfortably exceeding the gigahertz barrier, and you'll see the evolutionary leap they've made.
How a CPU Works
The rest of the video uses material from the book But How Do It Know, written by J. Clark Scott, a solid starting point for anyone who wants to learn more about how the processor and other components work, without ruthlessly struggling with complex terms. The video also shows the interaction between the CPU and RAM memory, the access to its addresses, the reading of data stored in those addresses (which can even contain other addresses, needed among many things to operate with external devices, such as a printer) and the application of instructions.
It also does not neglect more elementary aspects, such as the presence of the Control Unit, and another old acquaintance known as the Arithmetic Logic Unit. In total, the video extends for more than twenty minutes, and unfortunately there are no Spanish subtitles available. It does have English subtitles, very well made, with which you can use YouTube's automatic translation to follow the explanation. It's worth the effort!
Want to know more about processors?
Firsthand, you can understand how it works with this paper CPU or by building one yourself in your browser. Want something more advanced? LogicEmu to the rescue! You can also learn a lot by building an 8-bit computer.
