I/O ports have been in computers since the beginning of time, without them there would be no communication with the user, either to collect data or to transmit it back. Throughout history there have been different types of entry and exit ports and that is why we have made a collection of all of them, arranged according to the type of use.
One of the characteristics that define the PC above other platforms is its expandability. Thanks to its ports of entry and exit. Which allow you to connect all kinds of components and peripherals.
General characteristics of the inlet and outlet ports
The I / O ports are communication ports, which are responsible for transmitting a series of data between two ends, all of them have the following characteristics:
- A clock: This signal marks how often a data transfer is made.
- Data pins: The pins that transmit information from one side to another, there are reception pins, sending pins and Full Duplex that allow data to go one way or another. If there are several data pins on the port interface we will say that it is a parallel port, if there are few pins then we will say that it is a serial port.
It should be clarified that the fact that a port is serial does not mean at all that it is slower, since the amount of data that is sent and / or received will depend on their clock speed. The I / O interfaces as well as the rest of the logic in the processors have evolved over time and what, for example, was previously possible only with wide parallel ports, has reached the point that became possible with serial ports .
Ports of entry and exit used today
These ports are what you can find on PCs and motherboards that are sold today.
USB input and output ports
USB ports are the absolute standard for input and output ports, as they are used by a multitude of peripherals. Its origin, however, is outside the PC, since this is a version adapted to the PC and updated on the SIO port of Atari 8-bit computers. The SIO port served to avoid having to put an entire computer in its floppy drives as it happened in other 8-bit computers.
The USB standard appeared in the late 90s with the aim of replacing various ports on the PC, such as the Centronics or LPT1 port, the COM port, and the PS / 2 ports. A goal that took years to achieve due to the proliferation of peripherals with these interfaces. Its first version had a transfer speed of only 11 Mbps, its version 2.0 improved to 480 Mbps and it also became an ideal port for video transmission, thus retiring the IEEE-1394 or FireWire. As for its version 3.0, it allows data transfer at the speed of a SATA port.
USB comes in many forms, but the newest is USB-C which not only allows fast charging of peripherals and even entire computers. But also function as a DisplayPort. Seeing its history it is clear that the term Universal has it more than deserved.
HDMI video output ports
The HDMI port is the absolute video standard in televisions, it is an advanced version of the already abandoned DVI port but including the ability to transmit sound and playback of content in high definition with copyright protection systems. HDCP. It first appeared when component cable was found to not provide enough bandwidth for Full HD and both Blu-ray and streaming content needed some method of anti-piracy control.
Today it has been evolving in terms of its capabilities and bandwidth, allowing the transmission of 8K video and refresh rates beyond the classic 60 Hz.
DisplayPort video output ports
The other video output port is DisplayPort, but while HDMI is a standard for television manufacturers, DisplayPort is more geared towards the computer market, so this port is rarely found on televisions. Like HDMI it has had several versions, but it is more intended for use in a computer, due to things such as the fact that it supports a greater number of resolutions in its standard compared to HDMI and is designed for the use of several screens.
RJ45 or Ethernet ports
The Ethernet port of a lifetime, which allows us to connect at high speeds with our PC to the network, which cannot be reached by any type of wireless standard. Its permanence is thanks to its evolution where if years ago we talked about 100 Mbps connections, today we already have 10,000 Mbps or 10 Gbps interfaces.
3.5mm mini jack and TRS connectors
It is the port for connecting speakers and microphone par excellence. The connector has 2 variants, the first one supports mini-jack connections with 2 rings in which each ring corresponds to a stereo channel, a third ring means that the microphone can be used. Although there are systems that separate input and output in two different interfaces.
A variant of this type of connection is the TRS connectors, which allow several speakers to be connected in a positional system. Of course, with the limitations in bandwidth and sound quality
S / PDIF ports for digital audio
When DVD became popular, so did DOLBY Digital, which was the first truly positional system and therefore required much higher bandwidth. The solution? The S / PDIF or SONY / Phillips Digital Interface Format port. Which transmits audio in digital format through a coaxial cable in a single port.
Advanced multi-speaker systems such as 7.1 make use of these types of connectors. Which are much better than TRS. Not only for not needing so many cables, but for delivering higher sound quality thanks to the higher bandwidth.
PCI Express ports
The PCI Express slots are where we connect our graphics cards and M.2 NVMe disks today, as well as other peripherals although less used require this port. Designed as a successor to the AGP and the classic PCI, it is a standard that appeared in the mid-2000s and has evolved until now, where version 4.0 is already on the market, version 5.0 is on the ramp of launch and 6.0 has already finished its design. Each generation doubles the bandwidth for communication,
Its peculiarity compared to other I / O ports is that it inherits from AGP the ability to access the RAM of the system directly. Of course, with the corresponding control mechanisms. This is key for CPU–GPU communication and to be able to copy data more efficiently from an NVMe SSD.
Ports of entry and exit that have ceased to exist
These ports are hardly seen on the PC anymore, being replaced by ports that do the same task but with higher performance, better consumption or both. Although we can see them used in some motherboards today.
RS-232 or DB9 port
This port was used to communicate hardware in the era of mini-computers. Especially the terminals. It was adopted by the PC in the early years being the I / O port par excellence of peripherals such as keyboards, mice, modems and a long etcetera.
First it was replaced in use by the PS / 2 port as far as mice and keyboards are concerned, high-speed modems began to use more advanced ports such as ISA and little by little it was ending in disuse until being retired by USB. When that happened it was one of the most useless parts on a PC.
Centronics ports
The famous printer port, a parallel port that first appeared on IBM’s MDA graphics cards and later became part of the motherboard. It was withdrawn from the market as soon as the USB port appeared and it became so slow that it despaired. It is a 36-pin parallel port that was originally designed for printers and scanners.
Over time the Centronics port was replaced by the parallel port or DE9 port, which is a parallel version of the DB9 port, so it is based on the RS-232 standard. Since both are known as printer ports, they used to be confused, that is why we have grouped them in the same section.
VGA port
The VGA port was the quintessential standard for CRT PC displays, and it managed to live for almost 20 years, but it proved incapable of displaying good image quality on an LCD screen, so it was quickly superseded by standards such as DVI. HDMI and DisplayPort.
The VGA port is related to CRT monitors, but has also been used in projectors. Its disappearance is due to the increase in the use of digital video, which is much better understood with LCD panels, which by taking up less space ended up replacing televisions and monitors with analog signals.
DVI port
The DVI port was an attempt by VESA prior to DisplayPort to launch a successor to VGA. In reality, HDMI derives from this port, with the difference that DVI does not support HDCP content, it does not transmit audio and it did not evolve as HDMI has evolved. You can see it on televisions and monitors from the second half of the 2000s.
The DVI standard had 3 different types of connections, DVI-I could transmit signals in analog and digital, DVI-D only in digital and DVI-A only in analog. Each one with a different pin configuration. These differences not found in either HDMI or DisplayPort were one of the reasons why DVI didn’t have a longer run.