Target Disk mode for mac pro 2013?

We just got two new Mac Pro 2013 towers... is it possible to boot them in target disk mode? I started up holding down "t" and got the thunderbolt symbol. I don't have a thunderbolt-to-thunderbolt wire at the moment. I did try using a male-male USB cord... and out of curiousity, an HDMI cord to an adapter to my laptop.

I also read on some forum that starting up holding "t" allows you to choose a second monitor on some systems.

I was trying to partition the machine to see if I can use Bootcamp and/or install older systems (maybe? to the former, no to the latter). In the process of doing so I seem to have messed something up, and I want to restore the drive from an image I made before these disks couldn't be unmounted anymore...