The back of your PC is a rich source of connectivity. Ports and connectors exist for just about any device you can find, though some may be more obscure than others. In today’s USB-centric PC, it’s sometimes easy to forget that other connectivity options exist. Even USB isn’t just USB any longer.

Let’s walk through the plethora of connection types you could conceivably find on PCs, and their possible use. We’ll start with the most modern connections and work backwards. At the end, we’ll touch on possible connections you’ll see in future PCs.

While the examples here focus on desktop PCs, most of these connections are available on various laptop PCs as well.

Schizophrenic USB

USB used to be simple. You had USB 2.0 and… that was it. USB 1.0 connections existed for a brief time, but once USB 2.0 came along, with substantially better throughput, it became widely adopted. As with any widely adopted standard, variants appeared. Let’s look at some flavors of USB you might find, and how they might vary.

USB 2.0 is the standard port type. These days, mice, keyboards, hard drives, optical drives, printers and just about anything else can be found in a USB 2.0 flavor to plug into one of these ports. Even with the emergence of USB 3.0 (SuperSpeed USB), USB 2.0 is still the most versatile connection.

This particular type of USB port ships on certain recent Asus manufactured motherboards. This is a standard USB 2.0 port, and can be used as a normal connection to USB 2.0 devices. However, it’s also able to auto-install a BIOS. You need to copy a special BIOS flash program to a USB flash memory key, as well as the BIOS you want to install. Then press a button next to the port when the system is powered up, and the BIOS auto-installs. This is a pretty geeky feature, tailor made for hard core enthusiasts who may have gotten themselves into trouble with severe overclocking or other tweaks.

These types of ports are available on motherboards made by Asus, Gigabyte and possibly other manufacturers. It increases the available trickle current out of the USB port to charge up mobile devices like smart phones and tablets. This is in response to devices like Apple’s iPad, which requires more current to charge than the normal USB 2.0 port might supply to charge in a reasonable amount of time.

USB 3.0 is the latest version of USB, and is also known as SuperSpeed USB. It increases maximum throughput to 5 gigabits per second (625MB per second.) Most PCs implement USB 3.0 through a discrete chip built onto the motherboard, but some AMD chipsets have USB 3.0 built into the PC’s core logic. Intel will be building USB 3.0 into its core logic in its next generation Ivy Bridge chipsets.

USB 3.0 is backward compatible, so you can plug in USB 2.0 devices, but you’ll only get USB 2.0 speeds. Also, USB 3.0 cables are different than earlier USB cables, so be sure to get the right cable type for your USB 3.0 device, if your spiffy SuperSpeed USB gizmo didn’t include a cable in the box.

eSATA: Redundant, but Useful

High speed, external storage is critical for archiving and editing of digital video and raw digital photographs. You’d think USB 3.0 would fill that gap, but sometimes you need a little more performance.

Enter eSATA or external SATA. The latest eSATA connections can handle 6gbps SATA drives and connections, which is a little faster than USB 3.0. A variety of external SATA enclosures exist which support various RAID formats if you’re looking for redundant storage.

Networking Connections

The most obvious networking connection on desktop PCs is the ubiquitous Ethernet jack.

Gigabit Ethernet is built into most systems today, and if you have a wired house, there’s currently no faster network connection available, though that may change if 802.11ac wireless networking becomes a reality.

Some motherboards support wireless connectivity. Those that do now ship with 802.11n Wi-Fi on board, which does allow for throughput up to 600 megabits per second. And you can even occasionally find Bluetooth on board, as this image indicates. This allows easier integration with Bluetooth-capable devices, such as smartphones.

The Sound and the Fury: Audio Connections

In the old days, sound cards handled audio output and input chores for the PC. Today’s PCs have built-in audio, and may include several different audio connection types.

The most commonly used audio connections are the analog mini-jacks on the back of the PC. If you’re one of those rare folk with a multichannel PC speaker setup, you’ll use 3-4 output connections, typically green, black, orange and gray, to your speaker setup for multichannel audio. The pink one is the microphone input and the blue jack is the line input.

However, analog audio isn’t the only game in town. Some PCs also have digital audio outputs. The most common digital audio connector is the Toslink SPDIF output. Toslink is an optical connection using thin fiberoptic cabling originally developed by Toshiba (the “Tos” in Toslink.) SPDIF is more properly written S/PDIF, and stands for “Sony / Philips Digital Interface.” SPDIF is a signal level layer that can work with Toslink or copper as needed. It’s got enough bandwidth for uncompressed stereo, but compression is needed to support multichannel audio.

Other digital audio connections are also possible. Some USB-equipped devices, like headsets, can handle digital audio over USB. HDMI outputs and DisplayPort 1.2 can transport audio streams as well.

Display Connectors: Past, Present and Future

Of all the types of connectors, monitor connections seem to have the longest lifespan. It always surprises me when I unpack a Dell monitor to find the VGA cable pre-attached. What century is this again?

Systems supporting integrated graphics often still have VGA connectors. Most monitors shipping today still offer VGA as a connection as well, though we’re finally seeing some displays without that ancient analog connector. I see very few discrete graphics cards with VGA any longer, though most still ship with a DVI-to-VGA dongle should you need it.

DVI (digital visual interface) first appeared in 1999, while VGA emerged over a decade earlier, in 1987. However, both DVI and VGA will ride off into the sunset together in 2015. DVI was the first widely adopted digital connection for PC monitors, and will be superseded by DisplayPort.

DisplayPort seems redundant, given the existence of HDMI. But DisplayPort brings a few wrinkles to the table for PC monitors not available with HDMI. Licensing is one aspect – DisplayPort is licensed through the industry standards body VESA, and is royalty free. As of DisplayPort 1.2, you can daisy chain up to two high bandwidth monitors, plus the standard will support DisplayPort hubs for connecting even more monitors. DisplayPort also supports bitrates up to twice the throughput of HDMI, enabling support for very high resolution displays.

DisplayPort can also carry audio signals, up to 8 channels total, with an aggregate bandwidth of 49 megabits per second.

HDMI is familiar as an interface for HDTVs, but is also available on a wide range of PCs and graphics cards. HDMI 1.4a offers enough bandwidth to run a 1080p display at 120Hz, suitable for stereoscopic games and video. HDMI is also capable of carrying and audio signal, and most discrete graphics cards sold today can handle audio as well as graphics.

Mini-DisplayPort was originally popularized by Apple, but is included as part of DisplayPort 1.2. It’s common on current generation graphics card build with AMD Radeon HD 6000 and HD 7000 series graphics cards.

Mini-HDMI is less common on PCs, though you find it on consumer electronics devices such as digital cameras. However, you may find the connector on a few discrete graphics cards built with Nvidia 500 series GPUs. Typically, there will also be a mini-HDMI to HDMI dongle in the package.

Showing Their Age

A number of connectors still show up in a few systems, even though they’re rarely used by most home PC users. Some of these are more useful for businesses, who may need them to support older hardware still needed to help run some applications.

The most common of these older connectors is the PS/2 mouse and keyboard connector. Most motherboards that include PS/2 connectors offer two of them, though we’ve seen quite a few lately with just one, as this in this photo. Businesses that still have a lot of older keyboards or mice may still require this. I recently encountered and actual PS/2 mouse with a mechanical ball instead of an optical sensor at one small business.

FireWire, or IEEE 1394, is also still fairly common, though rarer on the newest motherboards. It’s useful if you have older camcorders or pro audio gear.

The parallel printer port is still occasionally found, even on some newer boards. Few printers really need this any longer, but a number of legacy devices in some businesses still use parallel ports, like point-of-sale hardware.

The 9-pin serial port is almost impossible to find any longer; this picture is from an old Pentium 4-based motherboard. Despite that scarcity, a number of laboratory instruments, point-of-sale devices and other hardware in some businesses require serial connections. In fact, you’ll find serial port pinouts available on many recent generation motherboards, but no way to actually connect them. You can buy PCI bracket adapters with serial ports that plug into these motherboard connectors, and a few boards do ship with those adapters.

Future Connections

We haven’t shown some connections you’ll likely see in PCs this coming year, or may already exist on some Apple MacOS systems. One example is Thunderbolt, the new high speed serial interface which first appeared on some Apple systems. It’s likely we’ll see Thunderbolt ports on upcoming Ivy Bridge based systems running Windows later this year.

The good news is that the variety of ports needed on the back of the PC will likely decrease over time. Even systems supporting integrated graphics may only have a DisplayPort and HDMI connector in the next year or two. Those systems will also likely have a Thunderbolt port, a number of SuperSpeed USB ports, audio and networking. Simplification in connectivity options is a good thing, since back panel real estate on a PC is getting scarce, particularly on small form factor PCs.

So what type of oddball connector is on the back of your system? Drop by and tell us what’s on the back of your PC that we haven’t mentioned.