All traces are 50-ohm configurations. Step response is shown on the left, and a 66-MHz clock waveform on the right. A slower driver will improve the ratio of line delay to risetime. A 15-ns driver is slow enough to damp out the ringing and reflections, whether we terminate the line or not. Slow Driver With 15-ns driver the step response overshoot and ringing problem goes away, but the response is so slow it won't work at 66 MHz.
Attenuation can help.
Using Attenuation Now let's try a both-ends termination scheme. With specialized receivers, this architecture can work wonders. With ordinary single-ended logic receivers, the diminutive received signal is useless. A partial termination can help calm, but not totally cure, the ringing behavior. Termination A partial termination, even if it's not the correct value, helps calm the reflections.