when i pushed the start button, imac beeped (3 times short beep, 3 times relatively long beep, and 3 more times short beep).
i thought the imac beeped when the system checked its hardware, so i changed the memory module to original one.(although it had passed 4 months after changing memory modules from original one) . . . . . nothing changed as predicted.
finally i went to apple store and asked what happened.
a "Mac Genius" answered to me "it's a firmware trouble. you have to rewrite the firmware."
after rewriting the firmware, my imac can start up without any problems.
but i don't know why the firmware broke.
i think the memory storing firmware is poor because i haven't changed the firmware for 3 month. it deteriorated by itself.(with heat?)
i suspect the other chips in my imac would make troubles soon.
