Mac computers introduced before late 2016 make a chime sound when they start up. Mac computers introduced after late 2016 don't have a startup chime, with the exception of MacBook Air (13-inch, 2017).
If there's an issue with your Mac, it might make one of these tones when it starts up:
- One tone, repeating every five seconds: No RAM is installed. If you recently replaced or upgraded your computer's RAM, check to see if it was installed properly. If the issue continues, contact Apple Support.
- Three successive tones, then a five-second pause (repeating): RAM doesn't pass a data integrity check. If you recently replaced or upgraded your computer's RAM, check to see if it was installed properly. If the issue continues, contact Apple Support.
- One long tone while you hold down the power button: An EFI ROM update is in progress. This applies to Mac computers from before 2012.
- Three long tones, three short tones, three long tones: EFI ROM corruption is detected, and your Mac 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.
- iMac Pro (2017) doesn't have EFI ROM tones.
- 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 on startup can make your Mac function in different ways. To learn more, see Startup key combinations for Mac.