Three Displays On My Macbook Pro

I've often heard that you can never be too rich, too thin or have too much monitor real estate. OK, I might have added that last thing myself. I'm definitely in no position to test the first two assertions, but thanks to the USB display adapter I recently purchased for my Macbook Pro I'm better able to test the third.

I purchased my adapter from OWC (Other World Computing) here, but I've since discovered what appears to be the same hardware available from Amazon here for about $20-$30 less. I verified that the one I purchased from OWC matches the model number of the device on Amazon, USB-1612. Here is the manufacturer's product page. It's possible the one on Amazon may only come with Windows drivers, since the product was apparently Windows-only initially. If that's the case you can download OSX drivers here. The CD that came with mine had both Windows and OSX drivers. As of this writing, it appears that Linux is unsupported. I've included a picture to give you an idea of the relative size compared with an iPhone, the handiest reference object I had available.

When I'm working on my Macbook Pro at my desk, I have an Acer 24" monitor running at 1920x1200 attached via DVI. It's a nice, large monitor, but I also have an older Dell 20" widescreen monitor which I like to use in more of a "tallscreen" orientation. The monitor can be rotated 90 degrees which is useful for certain applications (primarily reading ebooks, technical documents or long news articles - but it also comes in handy when reviewing credit card and bank statements online). Of course, the Macbook only has one external display port, so ordinarily there is no way to use both monitors at the same time. This device allows you to add additional displays (up to 4 in OSX, or 6 in Windows) via USB ports. I only tested it under OSX 10.5.7.

So, what's the verdict? Overall, I'm very pleased with it and it meets my needs, but there are some limitations you should be aware of, and my experience hasn't been problem-free.

The initial installation was fairly painless. I installed the OSX drivers using the supplied CD and restarted my Mac. I then connected the device to my USB hub. One nice touch is that the device draws its power over the USB connection, so there's not a separate power adapter to plug in - just the USB cable and the monitor cable (in my case a DVI cable). It comes packaged with a DVI to HDMI adapter as well as a DVI to VGA adapter - I didn't use either of those. As soon as I connected the device the new display was recognized. I just needed to bring up the OSX preference pane to rotate the image 90 degrees to match the orientation of my monitor, and I was in business! Everything was functioning properly and I picked a special wallpaper for my "tallscreen" monitor. But, I had a Safari 4 update pending, so I decided before I did anything else, I would go ahead and apply that update. It required a restart of the system, and that's where my problems began.

After rebooting, the system seemed to recognize the display, but the attached monitor was completely blank. The green light was illuminated on the monitor, indicating that it was receiving a signal, but the display was completely black. I tried unplugging/replugging the device, running "detect displays", and even rebooting again, none of which fixed the problem. After searching online for a bit, the only thing I could find was this link which didn't exactly match my scenario. The troubleshooting FAQ refers to problems with an already functional installation that may occur after applying the OSX 10.5.7 update. I was already running 10.5.7 before I initially installed the device. However, I figured it was possible that the browser update might have updated some system file, so with nothing better to try, I followed the suggestion, which basically involved uninstalling the drivers, rebooting, re-installing the drivers, and rebooting yet again. It was annoying, but it fixed the problem. Not able to leave well enough alone, I decided to reboot again, just to make sure everything was stable. I got the same symptoms - monitor getting a signal but no image being displayed. I did the uninstall driver/reboot system/reinstall driver/reboot system dance again, and once more the display came to life.

At this point I was getting pretty frustrated. Doing this dance every time I need to restart my Mac was not going to be acceptable. I did a little more poking around on my system, and launched the Console app, wherein I found this message repeating over and over:

DisplayLinkManager[739:65c3] Could not establish GA communication 0000044E

Often, I find that if you search for an error string on Google, you can find one or more people who have had the same issue, often with a solution, but in this case I had no such luck. I re-read the FAQ and decided to try that oft-suggested bit of OSX voodoo which is to run the Disk Utility program and repair disk permissions. In all the time I have been running Macs (about 4 years now) I can honestly say that although performing that ritual usually finds some permissions problems and fixes them, I have never had it actually cure the symptom that prompted me to repair permissions in the first place. Apparently this instance was the exception that proves the rule. After repairing permissions, and rebooting the system the display continued working. I rebooted a couple more times just to be sure, and the display came up fine both times, and I have not at any problems since.

What are some limitations of the device? As I mentioned previously, if you want to use this under Linux, as far as I can tell you are currently out of luck. Also, it only supports two resolutions: 1600x1200 or 1680x1050 (which is what I'm running it at - with the image rotated 90 degrees so that I can run it in portrait mode). At least on the Mac, it doesn't support OpenGL acceleration, which means certain things won't run on the display, such as video editing in iMovie. Also, only Intel Macs are supported. One other limitation that I ran into was that Crossover for the Mac doesn't seem to behave well with it. I tried moving applications running under Crossover onto the display, but as soon as I finished dragging the window, OSX became unresponsive. I could still move the mouse pointer around, but I couldn't switch focus to any application (no matter which display it was on), nor could I bring up the system menu or the "Force Quit" dialog. My only recourse was holding down the power button to reboot the system. I encountered this behavior consistently, and could not find any fix or workaround. Annoying, but I don't use Crossover that much, and as long as I remember not to move it to that display, it's not a problem.

After getting the kinks worked out, I'm pretty happy, and it's serving the purpose I had for it. I do wish I had known I could get essentially the same device for $20-$30 cheaper from Amazon. Ah, well -- live and learn. Here's a picture of my three display setup (one of the displays is the built-in display of my Macbook Pro). You may notice the monitor in middle of the picture looks a little screwy - it's actually a composite image I created using an iPhone app called Pano and I'm not particularly skilled in making those images look quite right.