I have a mid-2011 27" iMac and have a weird startup problem at the moment. When I try to boot I get a startup chime as follows: 3 beeps followed by a 3 second break followed by 3 beeps and it just keeps looping in the same pattern.

I did check this Apple Support page about startup tones, but my situation is not listed. It is very similar to the RAM failure tone, except that it's 3 second pauses for me not 5 as described by Apple.

Should I assume that the 5 seconds is not literal and it is in fact a RAM problem?

  • Thank you for your advice. Yes, I am sure - it's a very irritating startup chime. I think Monomeeth's answer nailed it! – user205310 Oct 22 '16 at 11:15

No, you cannot assume that. This repeating startup chime with the three second pause between the three tones is an indicator that you are trying to boot your iMac from a non-supported operating system.

The 27" mid-2011 iMacs originally shipped with Mac OS X 10.6.6, and later shipped with Mac OS X 10.6.7. This iMac will not run from Mac OS X 10.6.5 or earlier. However, on the positive side, it will run all version since, including macOS Sierra.

As an aside, it is strange that Apple hasn't documented this on the page you referenced.

Hope this helps!

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  • Thank you so much for your very prompt response. Yes, I was trying to boot from an external rescue disk running Snow Leopard 10.6.1, so your answer fits. – user205310 Oct 22 '16 at 11:13

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