50g Random Turn ON

[TravisE]

I've noticed the strange TICKS behavior myself, and I sort of wonder if there's some “tick synthesis” going on that tries to simulate the 8192-tick-per-second rate even though the hardware doesn't directly provide it. (I've read of a similar concept used to generate the clock signal for modern CPUs from a master quartz crystal running at a much lower frequency than the CPU's actual rate). This could be the source of jitter, and maybe there are some bugs/quirks that cause occasional very large jumps that seemingly shouldn't be occurring. I figure that a small, constant jitter would be expected for such a setup, but it doesn't seem to make much sense for the clock to ever occasionally jump several whole seconds at a time in either direction.

I don't remember for sure, but it seems like I recall that the jitter appears worse if the CPU is set to run at rate other than the default 75 MHz or whatever it is. Another observation I've made before is that CLKADJ, when given a non-multiple-of-8192 increment, initially appears to work for a fraction of a second, but then something apparently “resets” the clock so that the effective adjustment resolution is only a multiple of 8192.

This is just a guess, but I wonder if the system somewhere maintains an internal, high-precision concept of what time it thinks it is, which gets periodically “refreshed” from a hardware clock (which might have a much lower timing resolution). Maybe the two tend to get out of sync at times for some reason until the system eventually updates one clock's time from the other, causing apparent jumps.