Except there are Thunderbolt-to-PCIe enclosures, which come with their own set of problems (latency, hotplugging, I/O memory range allocation, bandwidth, not to

Except there are Thunderbolt-to-PCIe enclosures, which come with their own set of problems (latency, hotplugging, I/O memory range allocation, bandwidth, not to mention cost). But I guess Apple can just say "we don't support those, take it up with the enclosure manufacturer". Drivers for Thunderbolt devices still are necessarily kexts and can thus take down the system without an obvious culprit. For this reason alone I'm surprised they went with it rather than supporting USB3 early on or that they didn't come up with something similar but altogether new, like they did with Lightning. They seem to be trying to cut down third party kext development, and aren't opening the sources for most of their own new kexts. Of course, with IOMMUs available in all Thunderbolt systems, they could have brought back the microkernel aspect of Mach for device drivers, but that would have been even more work.