Intel-based Macintosh computers such as the iMac (20-inch Late 2006) rely on a combination of
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Intel-based Macintosh computers such as the iMac (20-inch Late 2006) rely on a combination of tones and blinking LEDs to display Power On Self Test (POST) error codes.
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tones and blinking LEDs to display Power On Self Test (POST) error codes. If the computer detects out-of-specification memory or no RAM installed, the screen will be black and the power LED on the front of the computer will blink once a second to indicate bad or no RAM. Bad RAM can include physically damaged, the incorrect type, or not present. If the RAM is good enough to pass the POST test but it is marginal and cannot be used by the operating system, the computer will show a gray screen, three tones will sound and the power LED on the front of the computer will blink three times, pause, and repeat until the computer is turned off. The solution to both these situations is to install known good memory.
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If the computer detects out-of-specification memory or no RAM installed, the screen will be black and the power LED on the front of the computer will blink once a second to indicate bad or no RAM. Bad RAM can include physically damaged, the incorrect type, or not present.
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If the RAM is good enough to pass the POST test but it is marginal and cannot be used by the operating system, the computer will show a gray screen, three tones will sound and the power LED on the front of the computer will blink three times, pause, and repeat until the computer is turned off. The solution to both these situations is to install known good memory.
Power On Self Test (POST)
Intel-based Macintosh computers such as the iMac (20-inch Late 2006) rely on a combination of
tones and blinking LEDs to display Power On Self Test (POST) error codes. If the computer detects out-of-specification memory or no RAM installed, the screen will be black and the power LED on the front of the computer will blink once a second to indicate bad or no RAM. Bad RAM can include physically damaged, the incorrect type, or not present. If the RAM is good enough to pass the POST test but it is marginal and cannot be used by the operating system, the computer will show a gray screen, three tones will sound and the power LED on the front of the computer will blink three times, pause, and repeat until the computer is turned off. The solution to both these situations is to install known good memory.