3 Beeps when booting from external USB HD

scottchlee said:

I got the 3 beeps at startup when I tried to do a clean install of SL on my 2011 15" MBP from a external USB drive with Snow Leopard imaged on a volumn. I thought the 3 beeps mean that something is wrong with the RAM but I can boot just fine normally.

Any idea on how to solve this problem? Thanks.

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3 beeps? Is your hard drive self powered or is it plugged in? I don't know why I'm asking but I seem to remember this problem from an earlier thread...

Get the same 3 beeps when booting from USB

Hi, I get the same 3 beeps when booting from external USB HD.

Been trying most of the day to reinstall os-x on my spanking new SSD and as I have replaced the superdrive with a harddrive bay and the original HD that came with the macbook I have to install from USB device.

I was unable to find the DVD that came along the macbook so tried using an old 10.6 disc but that one gave me instant kernel panic when booting.
Then I got my hands on a 10.6.3 image that I put on a USB drive. This then give me the 3 beeps when trying to boot from it.

The HD enclosure I use is powered by USB, using two cables.
I'm on the latest 2011 macbook pro 13"

Hope someone with the answer stumble on this thread