How bad is 5V input for DE1 ?

If the GPIOs of the DE1 are driven by a 5V system, how bad is this in terms of violating the specs ?

It seems odd that the Cyclone II pins connected to the GPIOs do not have the PCI clamping diode option, when they could use them the most :confused:. So all that is left in terms of 'defense' is the GPIO series resistors ...

Any ideas ?