Using a Belkin OmniView SOHO DVI KVM with an Apple ADC Cinema Display

Posted at 9:48 AM on 29 June 2005

This is going to be a bit of a geeky entry in the old blog, so please consider yourselves forewarned. It's a bit of a long story.

Also, a bit of background. Since buying an iBook many moons ago, I've become a bit of an advocate for the Macintosh platform, and my main PC setup at home reflects this.

Nevertheless, I've still kept and maintained my old PC; it's perfectly satisfactory for playing the occasional game of Half-Life 2, but setting up and switching between my Mac and my PC is time consuming and fiddly: both computers need to be pulled out from under the table, the cables swapped around (video, audio, USB), and everything pushed back so that I can fit back at the table again.

When I've finished playing, the process needs to be repeated in reverse. After all, everything else runs on my Mac.

Needless to say, I have not been playing games on my PC very often. But that's not to say I haven't wanted to, I just couldn't face the hassle.

What I needed was a KVM -- a switch that would allow me to operate my two computers using just one keyboard, mouse and display. The only problem being that I needed a KVM that could handle two digital (DVI) inputs, which are frighteningly expensive by comparison to their (massively cheaper) analogue counterparts.

Anyway, this (annoying, to me) situation came to a head last week when I received a free copy of the PC-only game, "Far Cry", with some memory I ordered from Crucial. Searching the Internet, I found that the device I needed was available at a price I was (very, very grudgingly) prepared to pay.

And so, the Belkin SOHO DVI KVM and two sets of DVI cables were ordered.

It took about a week, but everything finally arrived on Monday morning, so after I made it back home from the office I set to work getting everything sorted. Opening the box revealed a good-looking, small and well-designed unit. Excellent! Everything looked very obvious. How hard could it be to get everything set up and working..?

After spending an hour or so tidying up around my computer, making space for the new KVM and suchlike, I was ready to start plugging stuff in.

This is where I ran into the first problem. Namely, the Apple DVI plug is simply too wide to fit into the Belkin device due to a severe lip at the back of the unit, right next to the output socket. To put it mildly, I was annoyed. I really wanted this to work! Grudgingly discounting a case-mod with my hacksaw, I tried prising off the DVI plug enclosure (Apple's enclosure is on the wide-side) and in so doing, managed to get it to fit.

Because the KVM is so small, the area in which to plug everything in is very cramped, which isn't entirely ideal as it makes it quite hard to plug everything in. Perseverance pays dividends though, and the built in cable-tidy does actually work quite well.

With everything plugged in, I was ready to go. I switched on my PC and my Mac, and waited for everything to boot. I was heartened to see that I could switch between both DVI inputs, with absolutely no degradation in quality whatsoever.

I was slightly less heartened by the KVM's constant beeping. And then my Mac shut down.

Something wasn't happy. Something was wrong.

As it turns out, the KVM was complaining that a USB keyboard hadn't been plugged into it, hence the beeps. Not a big problem, but certainly one to note. More seriously though, my Mac just kept shutting down shortly after booting. Nothing I tried (fiddling with the power management settings) seemed to work, although plugging the display directly into the computer directly worked just fine. Things were not looking good.

After spending ages searching the Internet attempting to diagnose this behaviour, I came across a mention of the problem in a video editing forum. The problem was with Apple's implementation of DVI, which differs from the published specification in one important detail.

Pin 16 of a DVI connector is known as the "hot plug" pin. Apparently. In Apple's implementation, this pin is set to "low" when a monitor is connected and switched on. In the DVI specification however, it should be set to "high". My Mac was booting up, getting the "high" signal and that the monitor wasn't switched on (or whatever), and shutting down.

The solution? Needle-nosed pliers. Yes, I had to take one of my expensive, brand-new cables and vandalise it a bit. Rip out the rogue pin, I read, and everything will be peachy. Well, heck, I'd already invalidated my warranty for one bit of kit, why not another thing too?

The top part of the DVI connector looks like this:

    _________
    | . | . |
    | --|-- |
    | . | . |
    |       |
    | / * / |
    | / / / |
    | / / / |
    | / / / |
    ~~~~~~~~~

(Pin 16 is marked as an asterisk).

Throwing caution to the wind (and lets face it I was sufficiently wound up by this point I would have tried anything), I found some pliers and ripped out the pin. Well, not so much ripped as twisted and yanked until it broke off. It took a couple of goes, and I had to re-align the neighbouring pins after I'd finished, but I finally managed it.

And it worked! Hurray! My Mac booted up, and stayed booted!

The only problem was now that the mouse didn't work on either the PC or the Mac. Aarrrrrgh!

So again, I fiddled, poked and prodded... finally discovering that plugging the mouse into the USB Hub part of the KVM solved the problem nicely -- for whatever reason, the plug in which you're supposed to plug the mouse didn't work.

All in all then, it wasn't a straightforward, hassle-free installation and it had taken me an entire evening of fiddling about.

But I do now have a working KVM. And after the initial pain and wailing, I can honestly say that it does work beautifully. Just don't ask me to set up another one ever again.

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