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This guide shows the various beep codes for older and newer generations of Macs.

Part 1: Products Affected (Power Mac, PowerBook G3, iMac)

The power-on self-test resides in the ROM of the computer. Only computers that are based on the ROM-in-RAM (New World) technology, such as the iMac, Power Macintosh G3 (Blue and White), Power Mac G4 (PCI Graphics), PowerBook (FireWire) and PowerBook G3 Series (Bronze keyboard) will generate these beeps. This test runs whenever the computer is powered on after being fully shut down (the power-on self-test does not run if the computer is only restarted).

If a fault is detected during the test, you will not hear a normal startup chime. Instead, the system will beep as explained below. If you experience one of these beeps, you should call your Apple-authorized service provider for additional troubleshooting assistance.

1 beep = No RAM installed/detected

2 beeps = Incompatible RAM type installed (for example, EDO)

3 beeps = No RAM banks passed memory testing

4 beeps = Bad checksum for the remainder of the boot ROM

5 beeps = Bad checksum for the ROM boot block

Part 2: Products Affected (Portable Computers, Desktop Computers)

The power on self-test resides in the ROM of the computer. This test runs whenever the computer is turned on after being fully shut down (the power-on self-test does not run if the computer is only restarted).

If a fault is detected during the test, you will not hear a normal startup chime. Instead, the system will beep as explained below. If you experience one of these beeps, you may call your Apple Authorized Service Provider for additional troubleshooting assistance.

1 beep = no RAM installed

2 beeps = incompatible RAM types

3 beeps = no good banks

4 beeps = no good boot images in the boot ROM (and/or bad sys config block)

5 beeps = processor is not usable

In addition to the beeps, on some computers the power LED will flash a corresponding number of times plus one. The LED will repeat the sequence after approximately a 5-second pause. The tones are only played once.

Note: In this case, a flash is considered to be 1/4 second or 250 ms or greater in length.