In some of the smaller devices with larger packages there will be entire banks of pins that are unbonded. PartGen will list all the pins in that bank as NC (No Connect) because the output of PartGen is based on the device model and these pinsare not connected in the device. This is technically correct.
In the Virtex-5 Packaging and Pinout Specificationthe general I/O pins for an unbonded bank will be listed as No Connect; however, the VCCO pins for the bank will not be listed in this way. This is because there are some circumstances under which you would connect the VCCO pins of an unbonded bank. This is described in a note for the VCCO pin definition which states:
"VCCO pins in unbonded banks must be connected to the VCCO for that bank for package migration. Do NOT connect unbonded VCCO pins to different supplies. Without a package migration requirement, VCCO pins in unbonded banks can be left unconnected or tied to a common supply (VCCO or ground)."
Therefore, although the VCCO pins are not connected in these devices, you may still want to connect them to a VCCO source for future migration.