What exactly is a CPU?

DatumTuesday, 29. November 2016 KategorieKnow How

The fact, that the CPU is the processor of a computer or Mini-PC is most probably well known. But what tasks does it actually have and what is hidden behind the terms clock frequency, bus system and multi-threading?

CPU stands for “central processing unit“ and describes the processor of a computer. The “central” in CPU is not by chance since it can be seen as the heart of a computer. In addition to specific labels, the clock rate tells us how fast a processor is able to perform operations.

Tasks of the processor

On the whole a CPU assumes three essential tasks:

Arithmetical unit

All data on a computer consist of numbers. To be more precise: Of zeros and ones. A CPU accepts commands, calculates the appropriate amount of data and as a result gives out a new binary code. The higher the clock frequency of a CPU, the more digits can be processed simultaneously in an arithmetic operation. Clock frequency, which also can be described as a rhythm, is expressed in hertz. One Hz means one cycle per second. This means for a so-called single-core processor, that at one gigahertz (in short: GHz) approximately 1,000,000,000 digits can be processed at the same time.

Control unit

A control unit is together with the arithmetical unit a main component of a processor. In addition to the processing input and output peripherals (such as printers, scanners, mice, keyboards, …) the control unit ensures that the single components of a processor can work together appropriately and also coordinates them. The control unit and the other components of a CPU are connected over the so-called bus system.

Bus system

The bus system is a kind of bridge between the individual components of a computer and provides for the exchange of data between them.

Note: The more hertz a CPU got, the faster is the computing speed of a processor (of the same processor family). But is the clock frequency the only reason for the speed of a CPU? If today only the above mentioned single-core processors were still in use, we could answer the question quite easily with a “yes”. However, since two-core, four-core, six-core, eight-core and even ten-core processor are used in the field of desktops (as of 2016), the strength of a CPU also depends on the number of cores.

This brings us to the next subject:

Multi-core processors

As mentioned earlier CPUs have been made faster by increasing the number of clock rates. We remember: A single-core processor with one GHz is able to calculate 1,000,000,000 digits per second. Thus with two GHz it would be 2,000,000,000 digits per second.

However, the mere increase of the clock frequency implicates that enormous temperature rises will occur in the processor. This already happens at a power of 3,00 GHz. The reason behind this is that a higher clock rate can only be achieved by increasing the voltage. The resulting resistance in the thin leads produces heat. This is not only extremely inefficient but also damages the CPU without sufficient cooling. For this reason developers came up with the idea of installing several cores on one CPU. Today we are familiar with dual-core, quad-core, hexa-core, octa-core and also deca-cores processors.

A particularly great advantage of the so called multi-core processors is that the individual cores are able to assume tasks parallel to the other cores. Modern software, for instance, automatically stores operations on the individual cores of a processor in order to achieve an even utilization. If a core is fully utilized, the open tasks will automatically be transferred to a core with free capacities.

A further advantage is the low power consumption of the multi-core processors. Thus, a dual-core processor consumes only half as much energy compared to a single-core processor. The reason for this is that a dual-core processor with an equal performance as a single-core CPU requires a lower clock frequency due to a lower voltage. Ergo: Less power consumption.


Multi-threading is the ability of a single processor core to perform multiple tasks at the same time. Thus, multi-threading strongly resembles the appearance of a multi-core processor. In other words this means: If a quad-core processor is equipped with two threads per core, the system recognizes a total of eight virtual cores and no longer just four real cores. The advantage here is clearly obvious.


Single-core processors have lost a lot of importance in the fields of desktop computers and mobile areas and already have been banished by most sales shelves. This is also because extensive software in the user area requires at least two processor cores. This leads us to the question, what progress and how many cores the future will bring with it. Let’s wait and see!

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Intel Core i5-6600T processor with 4 x 2.7 GHz in the spo-book EXPANDED Q170