This is what i got from Gigabyte on PCI-E 1.1
Thank you for your kindly mail and inquiry. About the issue you mentioned, since GV-N660OC-2GD belongs to PCI-E x16 interface and if your motherboard has PCI-E x 16 slot, generally speaking, you can use this VGA card in your system without problems. It will backward compatible with the PCIe 1.1 motherboard.
If you worry about hardware compatibility issue, we suggest you to purchase from a reliable retailer to be able to support for after-sales service.
Regards,
GIGABYTE