Computer Ports Tutorial

Just having a computer itself is not enough. You must have some way to attach external devices. Let's face it, without a monitor, printer, mouse, and keyboard, a computer would be completely worthless. All of the aforementioned devices and a host of others have to connect to a PC or a laptop somehow. Computer ports, normally just called ports, are the physical interfaces that connect these external components. Do not confuse these with network ports, which are virtual ports represented by numbers used for communication among networks. Remember, I am referring to actual physical connections on a computer. There are several different types of computer ports, the majority located on the back of a motherboard, while there are some on the front of most computer cases.

There are two types of ports: serial and parallel. Both are bi-directional, meaning data can be sent and received. Serial ports send information one bit at a time down a single wire. You can look at it like a two-way street. Every car in a lane travels in a single line. A parallel port carries data several bits at once on multiple wires much like vehicles on a multi-lane highway.

Serial ports were basically developed for devices that didn't require speed such as mice and keyboards, while parallel ports were used for devices that needed data to be processed much faster, like printers. The ancient DB 9 serial port has long been obsolete, but many motherboards still have PS 2 ports for a mouse and keyboard. These are round and color coded. The green one is the mouse connector and the purple for the keyboard. However, many people nowadays use a USB or wireless keyboard and mouse instead.

The parallel printer port (a.k.a IEEE 1284 or DB 25 because it has 25 pin holes) has practically been replaced by USB and are rarely seen on newer motherboards.


Most motherboards have mouse, keyboard, audio, video, USB, Firewire, and LAN ports. How many and what type varies from board to board. Common video ports are HDMI, S-Video, and DVI, listed on the monitor connector page. Audio ports are on the sound page. Here we'll take a look at LAN, USB, and Firewire.

LAN (Local Area Network) Port:
The LAN port is used to connect computers to each other in a network or to high-speed internet such as DSL or cable. It looks exactly like a regular telephone jack (RJ-11) except it's a little larger. It also goes by the name RJ-45 and uses an Ethernet cable for connecting.


The speed of a LAN port can be 10, 100, or 1000 megabits per second (Mbps). Most today support all three speeds. These rates are based on the type of Ethernet cabling that's used. Ethernet cables are divided into categories. Category 5, or CAT5, supports traditional 10 Mbps Ethernet and 100 Mbps (the 100 Mbps standard is called Fast Ethernet). Category 5e (CAT5e) and CAT 6 support 1000 Mbps. Since 1000 megabits equals 1 billion bits, this standard is often termed Gigabit Ethernet (the prefix giga means billion).

You may see some motherboards with dual gigabit LAN. This is just a board with two LAN ports, each supporting Gigabit Ethernet.

As with sound and video, you're not limited to using built-in LAN. You can by a PCI network card.

USB:
The Universal Serial Bus port is a small rectangular port and is the primary way used today to attach all kinds of devices via a USB cable. Devices must have a USB connector in order to connect to a USB port. Mice, keyboards, printers, and digital cameras are only a few of the many devices that can be USB. Below are four USB ports on the back of a computer.


The USB standards are USB 1.1 (obsolete), 2.0, and 3.0. The major difference is speed. USB 1.1 could transfer data up to 12 Mbps (megabits per second - the prefix mega means million). USB 2.0, also called High-Speed USB, can transmit a max of 480 Mbps. The USB 3.0 standard (a.k.a USB Superspeed), completed in late 2008, is 10x faster than USB 2.0, with a maximum rate of 4.8 Gbps (gigabits/sec, or billions of bits) and is backward compatible. In addition to superior speed, 3.0 is bidirectional and adds five additional wires - two for sending & two for receiving. The extra wires make the cable a lot thicker. It increases power output for charging USB devices, allowing you to use more than four devices per hub, and there's no power drain on non-active devices.

Although USB 3.0 exists, it has not made it to consumer products yet. This is expected to occur sometime in 2010. It's main advantage will be transferring digital content, more than likely replacing Firewire. But don't expect USB 2.0 to die anytime soon. There are still plenty of uses for it on slower devices such as printers, keyboards, mice, flash drives, etc.

USB devices are hot-swappable, meaning they can be plugged or unplugged without turning off the computer. Another nice feature is that you can attach numerous devices to a computer indirectly. Called daisy chaining, 127 devices can be connected via USB hubs. A USB hub is a small component that contains additional USB ports. You plug it into your computer, and immediately you can connect more devices. There are also PCI expansion cards with USB ports.

Firewire:
Firewire is similar to USB. Also known as IEEE 1394, 1394, or i.LINK, it was mainly developed to transmit data between digital devices. IEEE stands for Institute of Electrical and Electronics Engineers, the group that made the standard. Firewire is also a competitor with USB. Its speeds far surpass those of USB, making it ideal for transferring large files like audio and video. The first standard, called 1394a, has a data speed up to 400 Mbps. For this reason, 1394a is also known as Firewire 400. The second, 1394b, transfers data at a max of 800 Mbps. And as you might guess, it's called Firewire 800.

The typical port on a PC or laptop is Firewire 400. It looks a lot like USB except it's triangular at one end. To use a 1394, 400 connector in a 1394, 800 port requires a special cable. Devices must have a firewire connector in order to attach to a 1394 port. Like USB, they are hot-swappable, but unlike USB, devices can connect to each other without a computer (called peer to peer). You can also purchase a Firewire hub to attach several devices. A max of 63 devices can connect to each other.