I recently set up my old Mac mini as a server. I replaced it a few months ago with a Mac Pro, and wanted to muck around with OS X Server, taking advantage of some of its features, especially centralized Time Machine backups and software download and update caching.
I set up the server, but, since I’m running it headless – with no attached display – I could only view it in one resolution using OS X’s screen sharing feature. If the Mac mini runs headless, the GPU, not detecting any display, doesn’t activate.
There’s a way around this, however, and it’s pretty simple. I bought this CompuLab HDMI Plug with Remote Desktop Access, or 4K Display Emulator (the name is different on the two Amazon sites, Amazon.com and Amazon UK). This $25/£21 dongle fits in the Mac mini’s HDMI port, and emulates the presence of a display. With this attached, there are a number of different resolutions, from 1360 x 768 to 4088 x 2304.
I’ve chosen a low resolution, since running it at, say, 4K resolution makes interface elements so tiny that I can’t do anything. The only downside to me is that all the resolutions are 16:9; I’d have preferred something with less width.
This is a really simple solution to an annoying problem. If you’re running a headless OS X server, you should definitely get one of these. It will make your life a lot easier.