For the Kintex-7 Lab ES and Initial ES silicon, the QPLL VCO frequency range only supports 5.93 - 6.6 GHz. The Kintex-7 FPGAIBERT GTX core only limits line rates based on the data sheet specifications. The Kintex-7 FPGA IBERT GTX core does not limit line rate selections to match the above limitation, so it is possible to enter an unsupported line rate for the QPLL when using initial ES silicon.
Make sure that the QPLL is not used outside the VCO frequency range of 5.93-6.6 GHz in the Kintex-7 Lab ES or Initial ES silicon. If the IBERT core targeting initial ES or ES Lab silicon is used outside of this range, this might result in unreliable behavior of the transceiver.
If it is unclear on whether the device that is targeted is subject to this limitation, please refer to (Xilinx Answer 37579)for instructions on how to readback the JTAG IDCODE for the device. Refer to the JTAG IDCODE section of the answer record. For the Kintex-7 325T, a JTAG ID of 0, 1, or 2 will have this limitation. For the Kintex-7 480T, only a JTAG ID of 0 will have this limitation.