You find yourself using your laptop, you turn on Wi-Fi and suddenly you see how the battery starts to go down faster. But what if this was not only due to the Wi-Fi radio but also to the CPU of your PC? This is something that many people do not get to ask since many of us take for granted that the Wi-Fi in our PCs works by itself, without external help of any kind.
Wi-Fi can consume CPU
Wireless interfaces, as well as wired ones, make use of a series of communication protocols that must be respected for communication between both parties to occur. These interfaces are made up of a transmitter and a receiver, although in some cases they can be made up of a transceiver.
What is often assumed from the outset is that the parts of the processing related to the communication of the two parties are carried out by the hardware integrated in the same interface, but this is not always the case and in order to save on transistors, it is done that the CPU has to be in charge of executing these protocols, instead of doing it a specialized chip. This means that there are communication protocols that are not fully implemented by hardware and force the CPU to lose clock cycles for data transmission.
In the case of network interfaces, these usually have integrated the hardware of what was once a network card, whether we are talking about a WiFi connection, a LAN connection or any type of wired or wireless connection. However, this is not always the case.
HardMAC vs SoftMAC
The Wi-Fi standard, known as 802.11, has a MAC sub-layer that is responsible for making the access point and the different radios of the different devices communicate efficiently. However, as we have mentioned before, some data communication interfaces lack the necessary hardware, in this case the part in charge of the MAC sub-layer.
These types of devices are called SoftMAC, and they expect that the driver executed by the CPU itself will be in charge of carrying out this task. This is done to reduce costs, but especially since this simplifies Wi-Fi radio and allows it to be used for other wireless protocols. For example, many Bluetooth, 5G and WiFi radios are the same in some systems and it is one of the CPU cores that handles the different communications.
The HardMACs on the other hand have the complete implementation of a wireless interface, whatever it is, and although they cannot be updated they do not depend on the CPU to communicate the data. In some situations, the HardMAC implementation is preferable, especially in those where the data is sent encrypted from one end to the other.
Is PC Wi-Fi dependent on CPU?
The most widely used Wi-Fi radios are those of Intel, which are of the SoftMAC type as they do not implement the entire 802.11 communication stack by hardware. This is done in order to implement various communication protocols with minimal hardware. For example, the Intel AX 200 radio through a recent driver update can now support Bluetooth 5.2 without any changes to the hardware.
Since the Wi-Fi radio is from Intel, whose operation is optimized in part by the brand’s CPUs, Intel has the advantage to optimize the drivers so that its CPUs have an advantage in consumption when using wireless networks above AMD. One option for the assembly of PCs with AMD CPUs is to use Wi-Fi interfaces that are HardMAC, which happens in the case of some motherboards, but most prefer to accompany AMD CPUs with Intel wireless radios.