It's been a few years since I was programming those things but IIRC the TB 3frames are comparable to PCIe 3 frames (terminology is slightly different between the two).
The real thing is that TB3 only has four lanes while Intel's server (and I believe some desktop) chipsets have 16-lane PCIe. Not sure about the mobile chipsets (again, I no longer follow this as closely/ as I used to). So indeed you won't be able to pump data into an eGPU as quickly as you could a high performance internal one. Or perhaps we should add "yet"?
The real thing is that TB3 only has four lanes while Intel's server (and I believe some desktop) chipsets have 16-lane PCIe. Not sure about the mobile chipsets (again, I no longer follow this as closely/ as I used to). So indeed you won't be able to pump data into an eGPU as quickly as you could a high performance internal one. Or perhaps we should add "yet"?