[Chris Kenny] "[Chris Harlan] "This makes sense to me as these would be extensions of a PCIe lane, and is why I'm doubtful that you'll ever see a hub, other than hubs for other protocols."
PCIe supports star topologies itself -- that's how external PCIe expander boxes like the Magma work. And in any event, Thunderbolt isn't quite native PCIe -- PCIe is just one protocol that can be multiplexed over it. Even if PCIe didn't support star topologies, Thunderbolt controllers could disguise what was going on from PCIe devices.
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Again, I think you're mistaken and are mixing up abstraction layers. I'd like to be wrong. I'd like a hub. The one thing I know you are mistaken about in the above paragraph is "PCIe is just one protocol that can be multiplexed over it." PCIe and DisplayPort are the ONLY two bus level protocols muxed by Thunderbolt at that abstraction layer. Other protocols run on top of them. In my searches, I've found many references to hubs or potential hubs for upper level protocols, but NONE for anything at that level. ALL references at that level are to daisy-chaining. Check out the following Intel brief. Notice the focus on the daisy chain as the mode of connection.
http://www.intel.com/content/dam/doc/technology-brief/thunderbolt-technolog...
"With Thunderbolt products, performance, simplicity and flexibility all come together. Users can add high-performance features to their PC over a cable, daisy chaining one after another, up to a total of 7 devices, 1 or 2 of which can be high-resolution DisplayPort v1.1a displays (depending on the controller configuration in the host PC). Because Thunderbolt technology delivers two full-bandwidth channels, the user can realize high bandwidth on not only the first device attached, but on downstream devices as well.
Users can always connect to their other non-Thunderbolt products at the end of a daisy chain by using Thunderbolt technology adapters (e.g., to connect to native PCI Express devices like eSata, Firewire). These adapters can be easily built using a Thunderbolt controller with off-the-shelf PCI Express-to-“other technology” controllers."
