Chosen Solution
Can a non thunderbolt 27" monitor run off the iMac thunderbolt port as a second display? Apple tech support told me no. However since the old 27" monitor (non thunderbolt) works with the Macbook pro 17" with thunderbolt , why wonuld’nt it. Has anyone tried it?
I don’t see why there would be any difference in behavior between 2 different computers using the same port: the tech may have been trying to convince you to buy a thunderbolt display, or may have been referring to the display not operating at thunderbolt specs. I haven’t tried it, but if it works on the MBP, it should work on the iMac.
You cannot connect an older Mini DisplayPort Monitor DIRECTLY. However, if you connect another ThunderBolt device into the connector of the ThunderBolt Monitor and then connect the Mini DisplayPort Monitor into that - then it works. Yes, this is odd behaviour. It is worth noting that the 27" ThunderBolt iMac has two ThunderBolt connectors (so you can just plug the Mini DisplayPort Monitor into the other connector. Also worth noting that the 27" iMac can ONLY support two external displays (of any type). If you have two ThunderBolt Monitors daisy chained on one port the other port cannot drive another display (regardless of type).
