A bit of an update, as I've found out some more information:
The unit WILL WORK on Thunderbolt (without any throttling) at the OS login window. I can connect the unit with Thunderbolt, and the display will be detected and work fine. I log into OSX, and it still works fine (no throttling), however System Information still shows "No Device Connected" in the Thunderbolt info window. If I unplug the thunderbolt cable at this point, and then re-plug it in, it doesn't work any more and I get the throttled/slowness issue. It will only work (and not cause the throttling) if I plug in the monitor at the OS login screen.
Hopefully this information will help in some way. I'm going to try a new test assembly, just in case the SSD is causing issues (I can't otherwise figure how the thunderbolt port would work at OS login, but not in OS). Also, I don't know why the device window for Thunderbolt says "No Device Connected" even as an external display is connected and working (as I had plugged it in at OS login).
Really odd.
The unit WILL WORK on Thunderbolt (without any throttling) at the OS login window. I can connect the unit with Thunderbolt, and the display will be detected and work fine. I log into OSX, and it still works fine (no throttling), however System Information still shows "No Device Connected" in the Thunderbolt info window. If I unplug the thunderbolt cable at this point, and then re-plug it in, it doesn't work any more and I get the throttled/slowness issue. It will only work (and not cause the throttling) if I plug in the monitor at the OS login screen.
Hopefully this information will help in some way. I'm going to try a new test assembly, just in case the SSD is causing issues (I can't otherwise figure how the thunderbolt port would work at OS login, but not in OS). Also, I don't know why the device window for Thunderbolt says "No Device Connected" even as an external display is connected and working (as I had plugged it in at OS login).
Really odd.