What is a CPU?

Alan's Electronic Notes
Alan's Electronic Notes
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The Central Processing Unit, or CPU for short, is now the core component of electronic computers and one of the most dominant devices in the information age.

The Central Processing Unit, or CPU for short, is now the core component of electronic computers and one of the most dominant devices in the information age.

In a small way, the CPU is needed for all the computer software calculations that we use every day with our cell phone software, as well as for writing programs, knocking out code, and making PPTs on our computers.

In a big way, the manufacturing of spacecraft needs CPU for pre-modeling work; launch time, orbit, weather forecast, fuel all need CPU for simulation calculation; real-time tracking after launch, internal scheduling and handling emergency problems also need CPU for accurate calculation.

It can be said that in the 21st century, the CPU plays an important role in all aspects of life, work, and science.

The CPU's function is mainly to process data from computer software, translate human commands into machine language, and present commands to other devices in the computer, such as memory, graphics cards, and motherboards. In the whole computing system, it plays the role of "boss".

More figuratively speaking, the CPU is the human brain, and all information requires its participation or thinking.

The three major divisions that make up the CPU

CPU is composed of three parts: operator, controller, and registers.

The operator is mainly responsible for the execution of tasks, which can be understood as "workers", and its task is to be responsible for the direct calculation of relevant data.

The controller is similar to the "leader", whose task is to give different orders to the "employees" for different needs.

The registers can be understood as a liaison group between the controller and the operator, or as a "secretary", whose main job is to coordinate the controller and the operator.

The "department" of registers is very tedious, the controller will let it give commands to the operator, the operator computing too much data, will also let the register temporarily first deposit part of. Therefore, when there is too much data, the registers can not be busy, so they can only temporarily recruit some "temporary workers" - cache.

When the registers can't do their job, they call the cache to store the data. Of course, there are levels of temporary workers: Level 1 cache, Level 2 cache, and Level 3 cache. If the third cache is also exhausted, then it is given to the memory outside the CPU to cache.

In this huge sector, of course, there is a relevant behavior specification that allows the controller to give commands according to the rules. This behavior specification is the instruction set.

The instruction set may be different for different devices. For example, our computers use the complex instruction set x86, while the instruction set of cell phone processors is the condensed instruction set ARM. the biggest difference between these two instruction sets lies in the way the designer thinks about the problem.

Some people think that if I first give the person receiving the command enough training to master various complex skills (i.e., to implement corresponding complex functions in hardware), then later I can use very simple commands to make him do very complex things - for example, just say "eat ", he will eat, which is the idea of "complex command set".

But some people think that this will make things too complicated, after all, the person receiving the command to do very complex things, if you want him to eat vegetables at this time, then you have to retrain the skills of eating vegetables. In that case, why don't we divide things into many very basic steps?

From the use of these two instruction sets of equipment, we can see the difference between the instruction set.

The first is the performance. ARM is strong in efficiency, in some relatively fixed tasks of the application, its advantages can be brought to full play. The x86 is still the "big" in terms of professional software or comprehensive work.

The second is the ability to expand. Cell phones, until the product may be eliminated, we will not add their own expansion devices such as memory, storage, etc., the principle is good enough. The computer can be extended by bridging many devices.

Finally, the power consumption, X86 computer performance, but power consumption has been high, with Moore's theorem gradually failed, and now the performance is based on power consumption, moving hundreds of watts of power, is the national grid "long-term strategic partner". ARM side of the phone is probably only a few watts of power consumption, so it is more It is suitable for portable and mobile.

As for our daily interaction with the desktop is also seen on the boot as the operating system, you can understand it as special software, mainly to play the role of performance scheduling, file management, services, and visualization for the upper software.

How to make a CPU?

After introducing the CPU, then you must be wondering how such a complex component needs to be made. The complexity of making a CPU will be more than you can imagine.

Are you ready? Next, I will take you into the world of atoms, a world that cannot be seen by the naked eye.

The first step in making a CPU is to design the circuit diagram. As we all know, CPUs are super large-scale integrated circuits, and a reasonable circuit distribution is of paramount importance. Therefore, experts from design centers around the world will collaborate to design the wafer circuit of the CPU and complete the overall chip design of the physical mask.

The next step is to make silicon crystals. The raw material of silicon crystal is sand, after a series of complex purification will be sanded into a high purity of 99.9999% of the single crystal silicon rods, and then cut into small smooth slices. The wafer will be completed, and it will be etched with integrated circuits.

Impurities can have a serious impact on the quality of the CPU, so the environment for making wafers is 100,000 times cleaner than the operating room.

Then we have to carve the designed circuit on the wafer, with what carve it? The ordinary carving knife is far from that precision, clever scientists came up with the world's most delicate carving knife - light.

The wafer is evenly coated with photoresist, and then the circuit structure on the mask is printed on the wafer with ultraviolet light, and the exposed part is soluble and can be washed off. Then the unprotected part of the wafer surface is etched off, and billions of transistors are etched on a wafer the size of a fingernail.

It is not enough to have only transistors, different transistors have to have different functions, which requires the next step of the ion implantation process to apply different electrical properties to the transistors.

Here silicon, a semiconductor with unique properties, is used. The electrical conductivity of silicon can be changed by precisely controlling the substance implanted.

The process starts with the injection of doped atoms into the silicon lattice. These atoms are not uniformly distributed in the lattice, but at high temperatures, the doped atoms become uniformly distributed in the lattice.

Copper is the focus of the next procedure, where precise copper wires connect many transistors to form various circuits and perform various functions.

However, cleaning is essential in this process, as particles or impurities from the environment lurk at every stage of the manufacturing process. A barrier film is first applied to the wafer, which helps prevent short circuits and ensures the reliability of the circuit. Then copper is filled into the grooves and polished smooth. In this way, kilometers of circuitry can be carved out of the chip.

The final step is the packaging. After polishing the chip to meet the packaging requirements, the CPU is cut from the wafer with the finest cutter, SMD and soldered, and sealed with adhesive. After testing and sorting, the CPU can enter the market through each chip factory and then be sent to the hands of consumers.

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