i386/104867: Clock running at 2x speed of wall clock

[Bruce Evans]

On Sat, 10 May 2008, Jeffrey Brower wrote:

> I verified that the timecounter was indeed i8254 after I recompiled with
> that option and it still ran double time.

With the i8254 and precisely double time, just type in the correct
(doubled) freqency to "sysctl machdep.i8254_freq=..."  With the
APCI-fast timecounter, first fix the bug that the corresponding sysctl
is read-only.

> Everything I tried failed - even NTP gave up because it was constantly
> slewing.  No one could solve it and I never got an answer so I ended up

NTP can't reasonably handle a 2x error in the clock frequency.  Nor can
fixing a 2x error work if the error is transient.

Bruce