[c-nsp] Throttles on an interface

[Roy]

I have a PA-FE on a 7206VXR.  "show int" gives

Received 7798 broadcasts, 0 runts, 0 giants, 17 throttles
     393 input errors, 0 CRC, 0 frame, 0 overrun, 393 ignored

The throttles seems to be related to the input errors.  I also see
throttles with no input errors.  We have double checked (and replaced)
the cable and the ports without success.  Is there some sort of buffer
tuning that would affect this?

Roy