We call peripherals the components which connect to input and output busses from the computer via communication interfaces designed for this task such as USB, PCI Express, SATA. Its name comes from the fact that if we took the organization of a computer in the form of a diagram, then these would be found on the periphery. Its main work concerns the communication between the system and the user.
What types of devices are there?
Thus, we have three different categories of peripherals of a computer, depending on the use given to them.
- First, we have the Entrance like the keyboard and mouse that allow us to interact with the PC and send it things to do, either through gestures and clicks with the pointer, or with keyboard commands.
- Then we have those of Exitthe screen being the most logical of all, since it gives us real-time information about what is happening, but we can also refer to a printer or speakers.
- Finally we have those that require the two ways of working just like storage units such as hard drives, USB sticks, SSDs or solid-state drives. Also included in this case are expansion cards with coprocessors that relieve the central processor of certain tasks. In this case, graphics cards, sound cards, network controllers, etc. would also be included.
Keep in mind that a computer can operate without the need for peripherals, an example would be a device’s microcontroller, which recursively runs a program without an external user needing to enter data.
How are they related to the motherboard chipset?
The vast majority of them, although there are exceptions, are connected to the PC through what we usually call the motherboard chipset, although today it can be integrated into the CPU. Especially in low power systems. This part concentrates all the interfaces in a common point and communicates with the CPU. Its traditional name is Southbridge or Puente Sur, because in the schematics it was drawn under the memory controller or Northbridge. Other than that, it’s usually the traditional position where the chipset is usually found on a motherboard.
Curiously, although we generally use APU as a synonym for SoC, the latter really correspond to those APUs which also integrate the peripheral controller and the communication interfaces with the various input and output ports for the peripherals. However, when there is a large capacity for expansion, as occurs in a desktop PC, due to the interfaces with the peripherals of a computer, they are located at the periphery of the processor, to avoid an increase in the cost of the CPU or APU, most of them are placed in a separate chip in order to reduce costs.
How does a computer’s processor communicate with peripherals?
It depends on the architecture, because we have two basic ways to do it. The first is that RAM and peripherals are separated and therefore there are a series of input and output pins in the CPU with its own controller which allows communication between the two parts. However, this is no longer used as it involves sacrificing pins for data.
Currently, RAM is used by the processor to communicate with peripherals. For this, the chipset has a unit called IOMMU which manages access to RAM as well as a series of DMA direct memory access units. Since RAM is organized by memory addresses, specific parts of it can be assigned to specific tasks. Thus, it suffices to write in the parts reserved by the system for the peripherals of a computer so that the system processor or the peripheral receives the information.
interrupts
Some devices have the ability to perform what we call an interrupt, this consists of the CPU temporarily leaving aside the program running at that time to respond to an urgent request from said device.
This is what allows that when we move the cursor and there are thousands of processes running, we immediately see the pointer move on the screen or when we press a key, the text appears in the window on which we are writing at this moment or that our character react in a video game by pressing the command button.
Computer peripherals and their drivers
All devices come with drivers or a controller, which allows the system to communicate directly with them. When an application requests access to a device during its execution, it does not have the right to access it, but it is the operating system that performs this task. That’s why there are different drivers for Linux, Mac OS and Windows. Even your video game console or mobile phone has drivers, except that these are already in the system and therefore do not need to be installed.
The drivers of the various peripherals of a computer are not executed as one more program, but in the private and protected space available to the operating system, to prevent the injection of a program with malicious intentions which could put endanger the health of our PC and our confidential data. On the other hand, many devices come with configuration applications that are often confused with hardware drivers.
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