Comment 1 for bug 17589

ntpd can only compensate for a certain amount of drift (500 PPM I believe). I
have a system which is in a similar situation, and the problem needs to be
corrected at a lower level (getting the clock running at the proper frequency)
rather than by updating the clock more aggressively.

In my case, the hardware in question is a Soekris net4501:
http://www.soekris.com/net4501.htm