Build a Dummy Dongle for a headless Mac mini

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Update:

If you are running a Mac mini with an HDMI port, be sure to read our new post about the HDMI adapter for a headless Mac mini. The HDMI works much better for machines running Mavericks.

Original post below:

The other day, I asked on Twitter:

Anyone know why Google Chrome would render very, very slow on a headless Mac mini?

There were some good responses, and we decided it was probably the “headless” part of the equation and not the “Mac mini” part. I decided to connect a Mini-displayport -> VGA dummy dongle and sure enough, that took care of the issue.

A dummy dongle mimics a monitor being attached to a Mac. It will force a Mac to load the video driver and take full advantage of the GPU. We’ve been connecting these for years for those customers who use video intensive servers, or those who run a linux build that won’t boot headless. And now it turns out that Chrome (as well as other browsers) can really benefit from the video driver being loaded as well.

I reported back on Twitter that a dongle fixed the issue and had more than one request on how to build a dongle. I thought I had written this up years ago, but I could not find it. So here it is again. It’s easier than you think.

First, you need a mini-displayport -> VGA adapter. You can buy one from Apple or from Monoprice. You also need a resistor that can be bought from any sort of electronic store (Fry’s, Radio Shack, etc) I went with 85ohm.

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Then you’ll be connecting two pins on the VGA end. I went with the red out and the red return. That’s pins 1 and 6 for those scoring at home.

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That’s the extent of it. A couple things to keep in mind. I kept the wire long in this picture so it could easily be seen. Usually, I’ll trim it down just a bit, and then finish by bending it over and putting some tape on it.

Also, when you plug it into your machine for the first time, it will bring the resolution down real low. But hopping into System Preferences and changing the resolution is a quick fix.

Of course we have these available for any Macminicolo customers that would like them. (Just the cost of parts. No cost for the 9 seconds of labor.) There are only specific situations where these are really useful , but if need is right, they get the job done. For instance, if you do a lot of screen sharing with your remote Mac, this will offload much of that to the GPU and free up the CPU for getting things done.

If you have any questions (or better yet, if you know how to do this with the dongle that comes with the Mac mini HDMI->DVI) send us a note @macminicolo.

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