Forget DVI, HDMI; USB Displays Coming

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).

DisplayLink USB 1

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.

DisplayLink USB

A look in how DisplayLink exactly works.

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.

Samsung SyncMaster 940ux

SyncMaster 940ux does not differ from the regular business-oriented 19" displays offered by Samsung today. This LCD was the launch product for DisplayLink and the specifications haven’t changed since then. The business-focused monitor uses a TN panel and displays a resolution of 1280 x 1024 pixels. Other specifications include brightness of 300 Candela, a contrast ratio of 1000:1 and a 5 ms GTG response time. According to the spec, this display should feature 160 degree horizontal and vertical viewing angles, which were actually closer to 165 degrees according to our measurements.

DisplayLink USB

Two displays connected using a single USB cable.

Connecting the display is really something new. You only need to connect the power cord as well as a USB cable between the LCD and your PC. DVI and Analog D-SUB connectors remain unused. It gets more fun when you want to connect a second LCD: Take another USB cable and simply connect the second monitor.

We experienced a flawless installation and removal from all tested computers. You are disabling the display simply by using the Safe Remove Hardware option - the same way you work with USB flash drives and other USB hardware.

We have noticed that 720p HD video ran in our environment without noticeable stuttering, while playing games proved to be a smooth experience as well. If you play World of Warcraft or similar genre, strategies, or a Flight Simulator, you should not notice any difference to traditional displays. However, the bandwidth limits showed up in games such as Unreal Tournament III, Gears of War and Call of Duty 4: It seems that those games don’t like the tiling architecture. In Need for Speed: Pro Street we noticed issues with motion blur. Interestingly enough, the USN display worked well with other games such as Crysis and Half-Life 2: Episode Two. But our recommendation clearly is to stay away from a DisplayLink display, if you are running fast-paced games – at least as long as we are still waiting for USB 3.0.

We enjoyed several movies and had zero issues with movie playback, even in fast scenes. We were not able to detect a visible differences or disadvantages over DVI in titles such as Superman Returns, Terminator 3 and LoTR: Return of The King.

That, of course, means that you won’t notice any difference in everyday applications such as web surfing, Photoshop, YouTube, Excel, Word, Skype or a Media Player.

Given the fact that the USB controller requires CPU cycles to work, there is an obvious concerns how much of your CPU this technology will need. Two connected monitors resulted in a 30% load on a single Intel "Core 2" CPU core, or about 8% on a quad-core Core 2 Extreme QX6800 (2.93 GHz). Expect 50% of one Q6600 core being loaded in such a scenario.

If you are looking at a much less powerful CPU, such as AMD’s Turion 64 X2 2.0 GHz, the numbers were a total CPU load of 60-70% - or 100% of one core. That leaves you with only 30-40% of your available processing power. So, plan on using such a system with a powerful processor, ideally a high-end quad-core chip.

Sewell USB External Video Card

If you own a notebook, there is a pretty good chance that your laptop does not come with DVI output. It is a sad reality, but the majority of consumer notebooks feature only an old analog D-SUB connection and connecting your laptop to anything bigger than a 22" display usually results in a terrible picture.

DisplayLink USB

Sewell’s compact, $130 USB external video card.

Sewell offers an USB External Video Card, a small USB box that features a mini-USB connector on one side and a DVI connector on the other. Inside the box, you will find a DP-160 chip and a clock generator on the top and a single 16 MB EtronTech chip clocked at 250 MHz DDR (500 MT/s) at the bottom.

Working with this card was a true pleasure: Plug the USB cable into one side and the DVI cable into the other. Windows and Mac OS X recognize the device, but you have to have a driver CD available or download the latest driver software. This is less practical than the LCD display, which only required connecting the display with the computer. This is somewhat of a convenience drawback, especially if you consider that Sewell is asking for $130 for this part – quite a bit for a plastic box with a PCB in it. It works great, but it is simply overpriced. You can’t charge a premium without providing that premium feeling.

DisplayLink USB

This is how Device Manager looks like - you get a virtual graphics card and, consequently, virtual monitors.

If we put that aside, the experience with the device was flawless. Owners of a Macbook Air can use this part to get a second or third monitor. And what is even more interesting: Our screenshot was taken on a Dell 2407WFP-HC display in its native resolution: The DP-160 supports 24" native resolution of 1900 x 1200 pixels, meaning you can plug in one or two Apple Cinema Displays (one via a mini-DVI connector). You can handle displays in the standard Display Properties just like any other display else. During the test period, we had no issues with the product.


After using DisplayLink for several weeks, we got used to extending our notebooks to desktop displays and vice versa. The two Samsung displays are working great together and we found that using USB is more efficient than buying anti-cluttering kits. The removal of DVI, Analog D-SUB, HDMI or DisplayPort cables is something we welcome in a cable-burdened world of computers. Don’t get us wrong, DisplayLink is not without drawbacks. However, these flaws should go away as soon as more bandwidth is offered with USB 3.0.

At the end of the day, we believe that DisplayLink is a promising technology. Without doubt a company to watch.

  • dogman-x
    What about using USB to connect a PC to a Dolby Digital receiver? In other words, what if the receiver contained a sound module? Hardware encoding schemes like Dolby Digital Live or DTS Connect would be unnessary in this case. It would be great to forget about cheap sounding PC speakers and use a real sound system.
  • KyleSTL
    The device manager is showing a 9900GTX, yum! Someone knows something the rest of us do not. I hope the GT200 preview/review is coming soon.
  • spuddyt
    ooooooo thanks for pointing that out.... :D
  • sandmanwn
    It eats up entirely too much CPU cycles as is the usual downfall with USB.

    And what about audio? HDMI and DisplayPort send audio down the cable, I see no mention of that in this article?

    If audio is not included, what will the additional CPU loss be when that is added?
  • thomasxstewart
    So far USB Display Units have been given Poor rating. For Kyle: its GTX280, remember X. (New Slogan?)

    Anyway I doubt if I want my entire USB system hocked up with some Poor technology, Even USB3.
    One quick note. Nanotubes of Carbon are coming back in news with Korean co making unit soon. Also Copper Nanotubes seem to have promise, as crystal of copper has pointed end to its penta shape, thus field is enhanced by smallness of point energy radiates from.

    Signed:Physician thomas stewart von drashek m.d.
  • Joe_The_Dragon
    The faster USB 3.0 may come with even higher cpu load also does this work with sli / cross fire?

    How much work is the video card doing?

    Dose the bios screens show up over the usb link?

    Can you use this as your only screen?
  • HTDuro
    yep ... im sure, at last for me, that after ppl discover that the pc with this usb display got a 9900GTX .. who care about usb lolol we want review :P
  • KyleSTL
    9080492 said:
    So far USB Display Units have been given Poor rating. For Kyle: its GTX280, remember X.
    Actually, we're both right. 'GT200' is akin to 'G92' and the retail names are '9900GTX/GTX280' (I'm just reading from the screenshot) and '8800GT', respectively. But, yes, you're right the name on the retail boxes should say GTX280.
  • i agree, the 9900GTX is much more interesting than this cpu-cycle munching lame duck of a usb screen technology....9900GTX article please
  • thomasxstewart
    Thanks Dr. Kyle. Also Computer already have active display port So NOT only do you increase your cpu load by tonne; Joe d' dragon really goes thru some of weaknesses. Of course all you have to do is uninstall software. Some homes might like multi display option of being upstairs.