If you mean something like a 74ABT family, then I would expect about the
same variation as one might see from one vendor to another. But be careful
about different drive levels within the same family, i.e., 64mA vs. 24mA.
Some modern logic parts are built using a gate array process, in which case
many or all parts in that family may use the same exact I/O cell designs.
(A recent example I saw of this was a 74xxx16yyy 16-bit buffer.) In that
case, a family model ought to be about as accurate as one for a specific
part number in the family.
Same goes for SPICE as well as IBIS.
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