For some Virtex BG package devices, there are more pins on the package than in the BSDL file.
The BSDL file is a description of the die. The missing pins in the BSDL file are not connected (no-connect) to the die inside the package. Since the pins are not connected to anything inside the part, they are not described by the BSDL file.
For example, the V150 BG352 contains eight VCCINT pins labled as "no-connect"; they do not need to be driven. Please refer to the list of unconnected pins on page 3-37 of the Feb.16, 1999 databook, or refer to the "Virtex 2.5 V Field Programmable Gate Arrays" Data Sheet (DS003):
There are 5 Virtex BG package devices that fit this category:
Eight pins not included in BSDL file for V150 BG352 are the no connects:
B16, D12, L1, L25, R23, T1, AF11, AF16.