This application note seems to suggest that for high-speed signals clamping diodes can be used to deal with overshoots instead of termination:
To manage signal integrity issues and protect the input pin, follow the guidelines in this document [...]
Guideline: Use Internal PCI Clamp Diode on the Pin
The PCI clamp diode can sufficiently clamp voltage overshoot to within the DC and AC input voltage specifications when the bank supply voltage (VCCIO) is 2.5 V or 3.0 V.
I realize this will prevent the overshoot voltage from damaging the device, but I assume that "to manage signal integrity issues" means it is supposed to prevent signal reflections and ringing as well. Does it? AFAIK clamping diodes are very widespread in modern ICs, yet external termination resistors are common practice. What benefits does proper termination have, compared to this clamping approach?