[asterisk-dev] [svn-commits at lists.digium.com: [svn-commits] dhubbard: branch 1.4 r112689 - /branches/1.4/main/asterisk.c]

[Clive Nicolson]

Maybe what Asterisk needs is a pseudo timing driver, which on start up uses 
the best timing source it can see (ie zaptel or some system timer). If a 
better timing source appears then the pseudo driver switches to using that 
and if needed slips the timing it was providing until it is in sync with 
the new source, unless one can tolerate a one time jump to the new source. 
If the real clock source fails (ie a watch dog decides the source has not 
ticked within some short time of a lower quality timer) then it drops 
back to the next best timer, slipping, adjusting or jumping the phase as 
configured.

This is just a mechanism with timer sources and phase measuring to switch
clock sources, all simple stuff in the real hardware world. We can of 
course do better with software controlling the simple hardware!

Clive