AR# 37042: Design Assistant for PCI Express - Is 128-bit interface maintained when x8 Gen2 comes up in Gen1 speed?
Design Assistant for PCI Express - Is 128-bit interface maintained when x8 Gen2 comes up in Gen1 speed?
When using the Virtex-6 x8 Gen 2 product, if the core trains to Gen 1 speeds, does the 128-bit user interface remain 128 bits?
Note: This Answer Record is a part of the Xilinx Solution Center for PCI Express (Xilinx Answer 34536). The Xilinx Solution Center for PCI Express is available to address all questions related to PCIe. Whether you are starting a new design with PCIe or troubleshooting a problem, use the Solution Center for PCIe to guide you to the right information.
The x8 Gen 2 product always uses the full 128-bit interface regardless of what speed the link trains too. Also see (Xilinx Answer 36075) regarding information about packet straddling on the 128-bit interface.