Xilinx is the name of a maker of FPGA chips and as far as I know, never shipped any kind of application, such as a video card. So the video card was not made by Xilinx.

I know Lapis used Xilinx chips in their video cards. I am not aware of other video card makers who did.

But that's irrelevant until you try equill's last bit of advice. Do you have a NuBus card which you know works? If so, you should test the IIci's NuBus slots with it.