TG Daily Review - Waging standard wars is one of those annoying, but unavoidable flaws in today’s setup of the technology industry. In a perfect world, there would only be one standard defining a technology, but the reality is that in a diverse environment as IT, there will always be different interests and there will always be customers at stake, sparking different ideas of how a certain technology should look like: Take the display segment, for example, and take a closer look at the history of interfaces will reveal a huge mess of D-SUB 15/DB-15, BNC, HDI-45, ADC, DVI-I, DVI-D, HDMI, DisplayPort. Has anyone ever thought about the idea of reusing another interface with a proven track record and that has been around for quite some time to connect a PC to a monitor … such as USB?


Of course there have been such people. Among those were Quentin Stafford-Fraser and Martin King, who were driven by the idea that multi-monitor setups should be less so complicated, which resulted in the founding of DisplayLink back in 2003. Initially, they worked on the idea to use Ethernet to connect a monitor to a PC, but quickly shifted their focus to USB. The technology made its market debut in 2007 as part of the 19" Samsung SyncMaster 940UX monitor. Today, there are about 20 different products with DisplayLink chips available and there is more to come: We have no doubt that some of the products we saw down in Silicon Valley will create lots of buzz on gadget-crazy sites.


How DisplayLink works

An old saying claims that there is no such thing as free lunch. And that is also true with DisplayLink and its capability to transmit data between the PC and a monitor. To be able to squeeze picture through the limited bandwidth of the USB 2.0 standard (480 Mb/s), DisplayLink uses a tiling approach. The technology continuously checks the frame buffer inside a GPU for refreshed parts of the screen, using nothing else but a USB 2.0/Wireless USB connect to refresh the displayed picture. At least in theory, this would mean that you can connect as many screens as you want and you would only need a single cable. Or no cable at all (if you are using a Wireless USB hub).


DP-160 chip on DisplayLink PCB: This is the place where DisplayLink enables USB displays.

In terms of hardware, the tiling process is covered by a combination of DP-120 or DP-160 chips with DDR memory. DP-120 is DisplayLink’s debut chip and supports resolutions of up to 1440 x 900 pixels, while the more powerful DP-160 will officially support resolutions of up to 1600 x 1200 pixels (1680 x 1050 pixels if we are talking about 16:10). Physical limitations are either six daisy-chained 1280 x 1024 displays or several 1680 x 1050 monitors. In theory, you should have no issues connecting one monitor with an USB cable, and then connecting that monitor to another one.

 

Sadly, we live in an imperfect world and this technology is not without flaws. As you can imagine, rapid image movements impacts the display refresh rate. This limitation reveals itself especially in fast-paced games and movies. USB 2.0 and Wireless USB suffer from bandwidth limits and DisplayLink users simply have to deal with occasional stuttering in certain applications. However, we expect this problem to be resolved once USB 3.0 is introduced and supported.

On the software side, DisplayLink supports 32-bit Windows XP and Vista as well as Mac OS X. 64-bit Windows XP/Vista drivers are currently in their alpha stage with an expected final release date of Q3 2008 (August). Given these limitations we took a test drive of the technology using Windows XP Professional 32-bit and Vista 32-bit. We will be waiting for the 64-bit drivers and if you are wondering about Linux, we will have to disappoint you: DisplayLink is very cautious about its intellectual property, which means that it can’t open source most of its code. Don’t expect Linux support anytime soon.

The only real issue of these displays is a lack of HDCP support, since DisplayLink's encryption cannot encrypt encrypted packages. As a result, you will not be able to run HDCP-protected content such as Blu-ray movies on these displays. Dennis Crespo, DisplayLink’s head of marketing with an engineering head, said that the negotiation with the RIAA/MPAA - who are very protective of high-definition content - is an ongoing process: The problem here is that it is nearly impossible to explain that DisplayLink offers protected display path, we were told.

To give you an impression what experience the DisplayLink technology is offering, we decided to have a closer look at two monitors and two USB adapters. We were especially interested in the true limitations of the USB adapters. Samsung and LG are currently offering 19/22+7" and 20" displays. We had a chance to look at the Samsung 19” model.

Over the past couple of weeks, we have used not one, but two 19" Samsung SyncMaster 940ux monitors in combination with a Sewell USB to DVI External Video Card. A HP Pavilion tx1000 notebook and various testbed systems (mostly equipped with Intel Core 2 Extreme processors and Nvidia/ATI graphics cards) served as PCs.

Next Page: Samsung monitors, Sewell USB External Video Card and Conclusion