We recently upgraded to the new Mac Pro (late 2013) workstation. I have a 480GB SSD preloaded with all of my 3D/design software. I want to use this as an external OSX boot drive, not the internal. So, I plugged it into my older 2008 Mac Pro (at this point the SSD ran Snow Leopard) and booted with it. I then go to apple.com and get the free update to Mavericks 10.9.1 I wait... it says success.. I boot the external SSD on the old Mac Pro... Mavericks is working fine on this machine. All good up until now. I then connect the (supposedly Mavericks ready) SSD to the new Mac Pro via thunderbolt. The Mac boots from the internal and I tell it to restart with the 480 SSD I just updated on the old tower. It restarts and I get the "no symbol/circle dash" at startup. I don't get it. Basically I need to boot from the drive with all my acquired software (the 480GB SSD). I understand if I partition it and install Mavericks on the new machine it will erase everything. Not sure if it's just me or the free install of Mavericks, or a combination of installing on a Snow Leopard machine and transferring it over as an external bootable drive on the new machine, but I'm stumped. I may be overlooking an easy fix here, any advice or ideas are appreciated. Thank you!