Migration Assistant not working with SATA SSD on old Mac Pro
I am trying to use Migration Assistant to move files and prefs from my old Mac Pro (2008 model) to a new Mac Pro (2013). But MA fails to find the old OS (Mavericks) which is on a SATA SSD when using a FireWire/Thunderbolt connection and starting up the old machine in Target mode. It does find other copies of the OS on other HDs in the old Mac Pro (another, older copy of Mavericks on one HD and a very old copy of Mountain Lion on another.)
I tried using MA over Ethernet. Both computers are connected by wire to the same router. So I can see all of the old Mac Pro on the new one, including the SSD drive, but MA fails to find anything.
What can I do?
Mac Pro, OS X Yosemite (10.10.3)