Mac computers (except MacBook Pro models introduced in 2016) can produce several sounds when starting up. Your Mac should produce the familiar chime on start up.
If you hear one of these tones, it might mean there's a problem with your computer:
- One tone, repeating every five seconds: No RAM is installed.
- Three successive tones, then a five-second pause (repeating): RAM doesn't pass a data integrity check.
- One long tone while you hold down the power button: An EFI ROM update is in progress. This applies to computers made before 2012.
- Three long tones, three short tones, three long tones: EFI ROM corruption is detected, and the computer is in EFI ROM recovery mode.
Newer computers automatically recover from a corrupted ROM; when this occurs, a progress bar appears on the screen during ROM recovery mode. Don't disturb your Mac while the ROM recovery takes place. When recovery is complete, your Mac restarts.
If you need to restore the EFI ROM on certain Mac computers produced before 2008, you'll need to use a Firmware Restoration CD to restore the EFI ROM. Search Apple Downloads for the right CD image for your computer.
Pressing and holding keys when the startup tone sounds can make your Mac function in different ways. To learn more, see Startup key combinations for Mac.