I suggest you relax this test in kernel/time.c:
/* if the quartz is off by more than 10% something is VERY wrong ! */
if (txc.modes & ADJ_TICK)
if (txc.tick < 900000/HZ || txc.tick > 1100000/HZ)
return -EINVAL;
That should allow you to use adjtimex.
- Jim Van Zandt