Intel® Ethernet 700 Series
Linux Performance Tuning Guide
Check That Your PCI Express (PCIe) Slot Is x8
Some PCIe x8 slots are actually configured as x4 slots. These slots have insufficient bandwidth for full line rate with dual port and quad port devices. In addition, if you put a PCIe v3.0-capable adapter into a PCIe v2.x slot, you cannot get full bandwidth. The software device driver detects this situation and writes the following message in the system log:
If this error occurs, move your adapter to a true PCIe v3.0 x8 slot to resolve the issue.