Using linear adjustable regulators for VCCINT (1.25v), VCCIO (3.3v), and
VCCAUX (2.5v). VCCINT and VCCIO are dead on, but VCCAUX is 2.72v, 2.88v,
and 2.92v on the 3 boards I grabbed and measured. All boards seem to work
just fine.

The regulator output voltage is controlled by just 2 resistors. When I
changed one of the resistors to lover the voltage a bit, VCCAUX did not
change. This leads me to believe that VCCAUX is somehow being "back"
powered from the Xilinx chip. These voltages are present like this before
the Xilinx chip has been programmed. I have not removed the regulator to
measure current yet. Another thought was to put a shotkey diode between the
regulator output and the load to see if the Xilinx really is powering
VCCAUX, but I thought I'd post and see if anyone else has come across this
issue. Half the I/O banks are 2.5v and half are 3.3v if that makes any
difference.

Thanks - Dan