My guess is that the Intel Ethernet drivers are seen by the customers as very tried-and-true, and how to tune them is well-documented. AMD's Ethernet drivers ar

My guess is that the Intel Ethernet drivers are seen by the customers as very tried-and-true, and how to tune them is well-documented. AMD's Ethernet drivers are relatively unknown and unproven, and it's easy to imagine that they could perform worse. That could easily make up the difference in cost between an external PHY vs an external MAC+PHY.