  Glitch (sudden spinup) is a common phenomenon in pulsar observations.
However, the physical mechanism of glitch is still a matter of debate because
it depends on the puzzle of pulsar's inner structure, i.e., the equation of
state of dense matter. Some pulsars (e.g., Vela-like) show large glitches
({\Delta}{\nu}/{\nu}~10^-6) but release negligible energy, whereas the large
glitches of AXPs/SGRs (anomalous X-ray pulsars/soft gamma repeaters) are
usually (but not always) accompanied with detectable energy releases
manifesting as X-ray bursts or outbursts. We try to understand this aspect of
glitches in a starquake model of solid quark stars. There are actually two
kinds of glitches in this scenario: bulk-invariable (Type I) and bulk-variable
(Type II) ones. The total stellar volume changes (and then energy releases)
significantly for the latter but not for the former. Therefore, glitches
accompanied with X-ray bursts (e.g., that of AXP/SGRs) could originate from
Type II starquakes induced probably by accretion, while the others without
evident energy release (e.g., that of Vela pulsar) would be the result of Type
I starquakes due to, simply, a change of stellar ellipticity.
