For some years now I've been using a 3 screen workstation setup, consisting of a laptop (was Windows, now Mac) with external screen, and an additional screen for my Linux desktop, with Synergy providing cross-screen functionality.

This worked well enough, but recently I've found myself getting frustrated:

  • I use an Apple Wireless Keyboard, and the mapping of Fn/Ctrl/Option/Command on Linux is confusing
  • I use a Apple Magic Trackpad (highly recommended by the way), which doesn't have 3 Linux mouse buttons obviously, and which seems to scroll too fast on Linux
  • Synergy occasionally crashes, and the copy-paste sometimes does not work or does not support the content
  • I do most my work on the Mac, and not being able to use my third screen for my Mac is unfortunate

Some of these issues can be worked around, but it's not ideal. So I decided to hook up the third screen to the Mac too, and because it had no spare display ports, decided to try going over USB.

There are lots of options: StarTech, Diamond, EVGA, Kensington (specific link expired. Current options: Kensington video adapters), etc. I was looking for a model that was using a modern chipset, with good support, a good company attitude, and good availability.

I purchased a Plugable USB Display Adapter UGA-2K-A from Amazon UK. This adapter uses the DisplayLink DL-195 which will do 1920x1200 and 2048x1152 on DVI, and is well known and supported. The product comes with VGI and HDMI adapters and a USB cable, and is surprisingly compact at 4cm by 9cm.

The adapter needs a driver for OSX to recognise the display. The product came with a 8cm CDROM, which my MacBook's slot-loading drive won't take, so I headed over to DisplayLink's Mac Driver page and downloaded the 1.6 driver. OS 10.7 Lion will need a newer driver that is not yet available. Installation was trivial, but required a system restart. After that the display (a Dell Ultrasharp 2005FPW 20" Widescreen LCD Monitor) was recognised. System Profiler sees the USB device, but doesn't show a Graphics/Displays entry:

At that point you can re-organise your displays as per usual in the Displays pane in the System Preferences, which says my display runs at 1680x1050, the panel's native resolution.

In short: it works. Display quality is good. Moving windows is a little slower than on the main displays, but plenty good enough.

The hardware is passively cooled, so it's silent, but it does get a little warm, and needs airflow. It's bus powered, and no Extra Operating Current is displayed, so I assume power draw is OK. I couldn't see specifications about power draw, but note they advertise using up to 6 adapters concurrently.

Some things don't work. DisplayLink's website says:

Please note: This driver does not support 3D acceleration. Some features of Mac OS X applications that require hardware OpenGL acceleration, such as Keynote presentations and iPhoto slideshows, will not function properly

I ran into a couple of limitations:

  • The DVD Player window won't work on the display -- you can move the window onto it, but it moves itself back to a main display (cute).

  • Command-Shift-3/4 and Take Screenshot from Preview don't work on the display. Fixed in DisplayLink_MacOSX_V2.0 with OSX 10.8.4.

  • PinPoint draws a semi-opaque box around the cursor which is ugly and makes it hard to use:

    I've reported this to Lagente Software, who diagnose it as lack of support for advanced alpha operations by USB adapters. I've requested a feature to allow a user to disable PinPoint on specific displays. Fixed in DisplayLink_MacOSX_V2.0 with OSX 10.8.4 and PinPoint 3.7.6

All of which I can live with; I'll be using it mainly for web pages, email, text editting and monitoring.

Another minor usability niggle is due to the resolution differences between my monitors: when you move the pointer from a larger screen to smaller one, there are parts of the edge of the large window that fall outside the smaller screen, and won't let you move onto it; you have to move down the edge until you get to the top of the smaller screen. Because my screens are aligned at the bottom, I tend to hit this when dragging windows, since window title bars are at the top. If this sort of thing bothers you, get two identical screens, but make sure the adapter supports your native resolution. In my case the larger screen is a Dell U2711 (which I do rather like) running at 2560x1440, which exceeds the adapter's resolution.

What about my Linux use, I hear you ask? No, I've not given up on my workstation. I've moved the display onto another (VGA) input on the monitor, so that I can switch if needed. Most of what I do is command-line work, so I just ssh from Terminal. For GUI things I use Chicken of the VNC.

I still use Synergy too, to get to other machines, but by the time you're scrolling to screen number 5 it does become a bit silly, and it's not something I do often.

By the way, it looks like this product is supported under Linux too. From the manufacturer:

LINUX COMPATIBILITY: As of Linux kernel 2.6.31, this adapter has open source drivers in the kernel staging tree. As of 2.6.38, the driver was promoted to the main kernel tree. Configuration of X Windows for USB displays is still distribution and scenario dependent, however, and only for very adventurous users. Plugable is involved with Linux development work, see for details.

which sounds good.

Conclusion: recommended.