Display Port (DP) vs HDMI vs DVI vs Thunderbolt

If you’ve been monitor shopping lately you will have noticed that almost all of the newest monitors have a new connector. New monitors have VGA, HDMI, DVI and Display Port (DP). So why do we need yet another way to connect our computers to our monitors? Well, DP is a packet based connection with speeds that support up to four 1080P monitors connected on the same bus/lan/connection. Version one of the Display port standard was release in May of 2006. The current standard Version 1.2 was released in December of 2009.

DP has the potential to make it possible to connect your computer to multiple monitors with a single cable (provided the monitors have a DP in and DP out). There in lies the rub, monitors have a DP in but no DP out. Providing a DP out would require the monitor manufacture to add the extra electronics to essentially add a DP hub/switch.

The ASUS VE276Q is a 27″ computer monitor with DVI, HDMI, VGA and Display Port connections.

There are devices available from a number of manufacturers that will connect to a DP port and break out three DVI or HDMI ports. They run in the 200 – 300 dollar range as they have to electrically convert from the packetized DP bus to DVI/HDMI.

DVI and HDMI were developed in parallel with one group focused on home entertainment and the other on the computer industry. The DVI group disbanded in 2006 so that standard is basically frozen.Given the increase in monitor resolution and the associated increase in data speeds required to support the newer resolutions, a frozen standard is not likely to survive.

The EDID standard associated with HDMI was released as version 1.0 in 2000 and then updated to version 2.0 in 2006. Monitor and TV manufacturers continue to support both versions with some hybrids that support subsets of V2.0. The various implementation of the EDID standard have cause computer manufacturers to design in mechanisms to allow computers to ignore EDID reports. In some cases the only way to get an HDMI monitor to work correctly is to force the resolution. Both Nvidia and ATI have provisions for EDID spoofing designed into their Linux and Windows drivers and tools.

In 2008 Apple started supporting DP and has produced a number of higher than 1080P monitors that are DP connected. Apple has since migrated to a new interface called Thunderbolt. Thunderbolt was developed by Intel with technical collaboration from Apple.

Thunderbolt is backwards compatible with mDP devices in that a Thunderbolt connector can drive a DP display. The reverse however, is not true. Wikipedia says “Thunderbolt combines PCI Express (PCIe) and DisplayPort (DP) into one serial signal alongside a DC connection for electric power, transmitted over one cable. As many as seven peripherals may be supported by one connector through various topologies.” Thunderbolt uses the same connector as mDP but supports more than just monitors. The MacBook pro that I am typing on has a thunderbolt connected wired ethernet adapter.

Both ATI and Nvidia have cards that support DP and have added DP connectors to most of their multi-interface cards. Apple devices tend to have the mDP or mini display port connector on older devices and thunderbolt on newer devices.

DisplayPort 1.2 standard supports Multi Stream Transport (MST), allowing daisy-chaining of a maximum of six full HD (1080p60) monitors from two DisplayPort outputs on cards like the Radeon HD 6900 series.

What seems to be missing from the DP story is a way to physically connect three display port enabled monitors to one video card output. There is talk on the street about DP switches but there does not seem to be anything currently available.

HDMI will continue to be supported by the home entertainment industry but with the convergence of the computers, gaming and home entertainment, I expect to see more of the royalty free DP and thunderbolt technology showing up on all of these devices.

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