OK, I have spent some time on it

here is the result
http://kti.mff.cuni.cz/~maj/clockFast_OK.rle.
(They are twice as fast as the original, what is allowed by almost synchronised segments switching.
Translation tables are halved by segments switching rather to their on/off, so there is more garbage near the segments.)
I still don't like full sync of state changes ... states on right should be accessed later ... 0 is really small time on the clock. May be I will work on it sometimes in the future ... .
[edit]
Synchronisation among digits added, bug around 11-12 hours corrected.
I am not sure 2/3 reduction of tick time would be possible without reducing the clock size.
Even now the 0;9 states for last digit are accessed earlier by 8*60 ticks than other states to be able to properly block hour digit changes. PM/AM switch signal must be delayed by other 8*60 ticks.
[/edit]
OK, the width of states to segments tables could be halved so the synchronisation wait's could be much smaller. States automat could be reorganised to two rows what would made it narrower as well ... so maybe halving the tick time is still possible.
Hmm, the binary tree at the top is counterproductive as I add delayes later.
Much easier method works, which is well delayed without need of delaying labirints.
I would probably change the state logic. translation tables digits and PM AM mark.
(so no full block from original clock would remain ... but same microconstructions would be used often)
It seems to me the size of digits was chosen to match rather big state memory.
I am probably able to reduce the width to half what would allow ticks faster than rewriting a single segment of current size. But making segments smaller would work well.
... as a speed of light is limited, one must make smaller circuits to get higher frequency

.