Thunderbolt is basically PCIe in a cable. But the big issue you face is that PCIe is fast because the physical layer is so tightly controlled. Lane lengths to

Thunderbolt is basically PCIe in a cable. But the big issue you face is that PCIe is fast because the physical layer is so tightly controlled. Lane lengths to the same port are all approximately the same length. All the lanes are carefully shielded with a complex mix of grounded traces and large ground planes above and below. The length of the traces is limited to make sure the speed of light doesn’t introduce too much delay. So PCIe speed doesn’t come from fancy algorithms, but from fancy electronics, and a very tightly controlled physical layer. Extending that layer outside of a computer is tricky. Just like trains are much faster than cars, PCIe is much faster the DisplayPort. But trains require tracks, that are long and straight, and car don’t. Equally PCIe requires electrical connections that are short and straight, and DisplayPort doesn’t. Thunderbolt kinda splits the difference. It’s basically PCIe, but heavily downrated so it can handle being outside of a motherboard.