But regarding VBlank it states that it can have higher precision than MicroHz and Eclock.
Where does it say that exactly?
UNIT_VBLANK
This unit uses a strobe from the power supply to keep track of its
time or the "E" clock on machines without power supply strobes.
It is very stable over time, but only has a resolution of that of
the vertical blank interrupt. This unit is very cheap to use, and
should be used by those who are waiting for long periods of time
(typically 1/2 second or more). This unit uses a timeval in its
timerequest.
This means VBLANK is only good for relatively long delays. VBLANK is also lighter for the OS to handle.
So what's the limit that one should use EClock in favour of VBlank
It's quite clearly explained above.
