At high frequencies, the bus lines are signal transmission channels. Impedance mismatches at the ends of these channels can cause ringing – a form of noise – at a frequency corresponding to double the signal round-trip time. A 20 cm signal line will have a 250MHz ringing frequency, for example, since the period of the wave is 4nsec. The traditional method for eliminating unwanted reflections in a transmission channel is to dissipate the energy. You can do this by adding damping resistors in series with the lines from the output buffer, as shown here. You might be able to use a resistance value as large as 5kΩ, but be aware that if the value is too high, it can cause various types of subtle failures. Alternatively, you can insert a terminating resistor to ground at the receiving device. Adding the damping resistor is generally a better solution, though, because when you use a terminating resistor, you can get either excessively high voltage at the output buffer, or inadequate input current at the receiver because the Thevenin termination has been changed. Above all, remember that if you keep the transmission channels short compared to the signal wavelength, there will be minimum ringing, so no damping resistors will be required.