Hello SFBayJay, welcome to Intel Communities and thanks a lot for posting your inquire.
Currently, port multipliers are supported on the chipset side, on Intel® ICH9M-E, controllers. However, Intel® Rapid Storage does not support port multiplier and there are no plans to include such feature at this moment. I am sorry for the inconvenience.
Thank you so much for your quick response to my question! I'm not too technical, but I think what you're saying is that the port multiplier is (theoretically) supported by the hardware, but the Intel driver does not support the feature (and there are no plans for this in the future)?
Do I have it right?
If it is indeed a driver (software) issue, it's a real shame. I understand that controllers from competing manufacturers offer this capability.
Clearly this is a bit of an odd issue these days, as I'm sure USB 3.0 connectivity may be the preferred solution for most consumer applications.