5 and 10 MHz clock inputs

Because the device may *need* two different clocks and the device does not have the circuitry to generate one from the other. Now that's a little odd with 5MHz and 10MHz (a single flip flop), but not odd at all for a number of other frequencies.

I have a device that has a large number (4 to 9 depending on operational characteristics) of different clocks internally, and I supply two external clocks (not at any of the internal frequencies, amusingly) so the chip can generate them.

Cheers

PeteS

Impossible to say without knowing what the device is!

See above.

Dave :)

If you are talking about a piece of test equipment, different labs used different in house frequency standards.