What are some examples of computers

Computer interfaces

An interface connects systems that have different physical, electrical and mechanical properties. In every electronic system, defined interfaces are a prerequisite for interoperability with other systems, devices and assemblies. Interfaces are found wherever different systems have to be connected to one another. The interfaces form the transition from one system to another. This transition can be used for communication or data exchange. The specification of an interface defines common properties. This also includes a protocol for communication and data exchange.

The standardization of interfaces enables the dissemination of cooperating systems and the automation of electronic and digital systems. In computer technology in particular, interfaces are widely used to connect different devices and assemblies for input, output and processing. Standardized interfaces are also common in communication and network technology.
While the computer industry developed and standardized its own interface for each application in its early days, the trend is towards universal interfaces. For example USB and PCIe. Another trend is meta-interfaces, which combine several interfaces together in one interface. For example, the USB, the various USB signals and z. B. DisplayPort combined in a USB-C cable.

The specification of a typical computer interface contains information about

  • Transmission speeds
  • Transmission method
  • Interface cables
  • Plug connection (plug and socket) or plug strip and their assignment

The purpose of a specification or standardization is that different devices or systems from different manufacturers can be connected to one another.

Internal and external interfaces

A computer has internal interfaces that are located in the computer housing and external interfaces that are led out of the computer housing.
Internal interfaces connect systems within a computer. These interfaces are usually brought out on the motherboard as a socket or slot. Expansion cards are then connected directly or internal drives via cables. Some other interfaces are not brought out, but are located on the motherboard between the individual controllers.
External interfaces are led out of the computer housing. They connect systems or peripheral devices to the computer. The connection is made with a combination of plug and socket.

Example: External PC interfaces (2018)

Example: External PC interfaces (2020)

Bridge / bridge

If two systems are incompatible with each other and a common interface is not possible, a bridge is used between the two systems. The bridge ensures that signals, protocols and transmission systems are converted. For this reason, a bridge is sometimes referred to as a converter.

How this works can be illustrated with a PCI-to-ISA bridge. For a long time, the old PCI bus was used to integrate expansion cards into a computer system. For reasons of compatibility, the even older and slower ISA bus also had to be supported. A PCI-to-ISA bridge was used for this, which was a PCI device on the motherboard or in the chipset. There was an ISA host in it, from which the ISA bus was brought out and thus it was also possible to install older ISA cards in a computer system.

Current computer interfaces in comparison

interfaceTransfer rate (gross)Transfer rate (practice)
USB 1.0 / 1.11.5 Mbit / s0.15 Mbytes / s
12 Mbit / s1 MB / s
USB 2.0480 Mbit / s36 to 44 Mbytes / s
USB 3.2 Gen 1 (USB 3.0)5 GBit / s480 MB / s
USB 3.2 Gen 2 (USB 3.1)10 GBit / sapprox. 800 MB / s
USB 3.2 Gen 2x2 (USB 3.2)20 GBit / sapprox. 1,600 Mbytes / s
USB4 (Gen 3x2)40 GBit / s 
WLAN IEEE 802.11ac433 Mbit / sapprox. 50 MB / s
Gigabit Ethernet1 GBit / sapprox. 110 MB / s
SATA 6G6 GBit / sapprox. 560 Mbytes / s
PCI Express 3.0 x18 GBit / sapprox. 1 GByte / s
PCI Express 4.0 x116 GBit / sapprox. 2 GB / s
Thunderbolt 2 (PCIe-2.0-x4)20 GBit / sapprox. 1.25 GB / s
Thunderbolt 3 (PCIe 3.0 x4)40 GBit / sapprox. 2.5 GB / s

Legacy interfaces

Legacy stands for "heritage" and means something like outdated or obsolete. There are a lot of legacy interfaces in computer technology. The reason is that many peripheral devices often had their own interface. Today there are almost only USB, HDMI and various interfaces Variants with PCIe and SATA.

How are the specified transfer rates of interfaces and bus systems to be interpreted?

It is very difficult for laypeople to correctly interpret the information on the maximum data transfer performance of interfaces and bus systems.
This information seldom applies to pure data transmission, but rather in the so-called burst mode, in which the data are strung together without gaps. However, a few clock cycles of a data transfer are subject to a protocol overhead that has to be subtracted from most speed information in order to arrive at the actual transfer performance. That means there is a gross speed and a net speed. And that's only half the story, because the practically possible speed depends on the performance characteristics and capabilities of the controllers involved.
And then there is the fact that many PC components do not work fast enough to be able to utilize the maximum available transfer rate. Nevertheless, fast interfaces have advantages. New interfaces are usually exhausted after a few years of optimization and use with new applications, so that the speed has to be increased again.

How secure are interfaces?

Almost all peripheral devices and computer accessories are equipped with bidirectional communication. This means that there is communication in both directions between the peripheral and the host computer. At the same time, the functions of the peripherals are not implemented in hardware, but replaced by software that can be changed at any time. For example, through a firmware or driver update. This means that each peripheral device is becoming more and more independent. However, this also means that every device is vulnerable and can thus become a threat to the host computer.

An example: PCI Express allows direct access to the memory via Direct Memory Access (DMA). It is conceivable that an attacker could use this to smuggle in malicious code or to access data. Now the PCI Express is classically an internal interface for expansion cards. An attacker would have to gain physical access to and access to the machine. This scenario is conceivable but rather unlikely in practice. But, an external interface such as Thunderbolt enables access to storage via PCI Express. This makes it possible to attack a computer without opening it.

Another example: USB peripherals are usually integrated into a computer via plug and play. This means that the necessary driver is usually initialized automatically and, if necessary, installed beforehand. However, this also means that the user has no control over the function of these peripherals. The user does not notice whether the inserted USB stick is initializing other functions in addition to the integrated memory. For example, executing malicious code or recording keystrokes.

Internal interfaces for expansion cards

Interfaces for mass storage and drives

External interfaces for peripherals

Multimedia interface

Multimedia interfaces are usually external interfaces for screens and monitors for outputting and reproducing audio and video data.
Here, HDMI has replaced SCART, VGA and DVI from the entertainment electronics sector. DisplayPort is often found on graphics cards and PCs, but less often on notebooks. Except on Apple devices. HDMI is usually missing here. Some particularly slim notebooks only have USB-C ports, via which HDMI and DisplayPort signals are output.

Radio interfaces

With radio interfaces, radio technology replaces the cable connection between a computer and the peripheral device.
The wet dream of visionary computer manufacturers envisages that all cable connections for data transmission will be abolished.
The disadvantage is that radio connections are generally slower and more susceptible to interference.

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