FPGAs usually need their bitstream (analogous to firmware) loaded after power-on, so either there is a flash chip on the device that contains it, or it is loade

FPGAs usually need their bitstream (analogous to firmware) loaded after power-on, so either there is a flash chip on the device that contains it, or it is loaded over the PCI bus from the host machine via a software driver. Either way you'll likely need to reverse-engineer and modify the firmware and host-side device driver. There are often better choices, such as dev boards, to play around with FPGAs.