Solution for Mac OS system 10.10.3 boot speed too slow

Method One:

Completely shut down the machine. Press the Power key, then press and hold COMMAND + OPTION + P + r at the same time, press and hold, hear duang after the boot sound do not let go, repeatedly duang 4 times after letting go.

Method Two:

System Preferences--boot disk--Select your system's Startup disk--restart

Method Three:

completely shut down and power on, and then press and hold the option+control+shift+ power key, about more than 20 seconds, the charger light will change, and then re-boot can be (but this method is not very useful, but is the Apple customer service recommendation, believe there is a certain reason)

Solution for Mac OS system 10.10.3 boot speed too slow