Ok. This is the solution that worked for me.
On the Tanberg support site there are no “Mac Drivers” for the LTO-4, only PC drivers. On the Intel Macs the data retrieval software (Retrospect) has built-in drivers to allow the LTO-4 to talk to the Mac.
Where I was running into trouble was my operating system. For the LTO-4 to communicate to my MacPro I had to upgrade to Retrospect 10 even though my Mac OS 10.6.5 is NOT compatible.
Retrospect 10 only works with Mac OS 10.6.8, but as soon as I installed the upgrade to Retrospect 10 I could access the LTO-4 with the older software Retrospect 8. There must have been some drivers or firmware installed that helped Retrospect 8 actually see the drive.
So, in short, after I installed the ATTO UL5D drivers and all the other standard stuff I had to buy the latest Retrospect Software and use an older version (Retrospect 8) in order for the LTO-4, UL5D and MacPro to live in harmony.
THE END….
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