I have an 8X PCIe core in a Virtex6HXT (version 2.5, the latest in 13.4). It's configured for Gen2 but it's coming up Gen1. lspci -vvv reports that both the core and the board are Gen2 capable. I've looked at the PIPE interface in Chipscope and the board is advertising Gen1 speeds only. Xilinx support said that there is an issue with Sandy Bridge chipsets and that something had to be done in the driver, however they didn't know the specifics. Has anyone gotten V6 to run at 5GT on a Sandy Bridge? What did you have to do to make it work?
lspci -vvv
01:00.0 RAM memory: Xilinx Corporation Device 6028 Subsystem: Xilinx Corporation Device 0007 Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-