I have the requisite model iMac -Late 2009 iMac, and a brand new PC build employing AMD Threadripper and a GTX1080. I would like to use the iMac as a display in target disk mode from the PC/
The GTX1080 outputs to three DP's(DisplayPorts) and an HDMI. I have tried TDM using a DP to MDP(MiniDisplayPort) cable but have not succeeded in getting past the floating Firewire logo that TDM shows on this iMac build.
I see on Apple's forums it is specifically mentioned that MDP to MDP cable is to be used, and yet, I can find no evidence on the web to suggest that there's any actual difference in the data transmission between DP & MDP.
Is this configuration supported?
Best Answer
Target Disk mode is booting with a T and the OS not running. You will see a FireWire / USB / Thunderbolt icon in this target mode on supported iMac.
Target Display mode has no icons and needs the Mac OS to be running and is entered with either Command - F2 or Command - Fn - F2 keys.
The link above has all the steps to qualify / check your connections and requirements.