I have this little box called the Kanex XD HDMI to Mini-Displayport converter. It works perfectly with a lot of machines (tried it with a Macbook, PS4 and Xbox 360), but some devices don't seem to be supported and I'm wondering why.
One of the devices is the Playstation 3. I know the PS3 has trouble with its resolution, which means you have to reset holding some buttons etc. etc., but even that doesn't get it to work on my iMac in Target Display Mode.
The most recent problem I've run into is with the Raspberry Pi. Yesterday, I installed Raspbian on it while it was connected to my tv. This worked perfectly, if we ignore the weird resolution of 18##x9##.
Which made me wonder: Does the iMac only work as an external display in TDM if the device changes its own output video to 1280*720? Does anyone know a bit more about this function of the 27" iMacs 2010 (and any iMac after 2011 if I remember) who can explain how exactly TDM works or is supposed to work?