回答“3 beeps on start up”NEWS FLASH for MacBook Air users with 3 Beeps at startup!!! On a hunch, as I have noticed my MacBook Air has overheated in the past, I opened mine up to check the THERMAL PASTE. Made no sense that DRAM of any sort would fail after 15 months. When I got down to the logic board, I inspected the 8 visible 1 gigabit chips visible. The solder joints appeared pristine. Nothing else appeared burned, fractured, loose or disconnected. I then removed the heatsink I found the thermal paste dried and hardened! I carefully removed all of the old paste and then applied new high quality thermal paste. I then reassembled the machine. Rebooted and NO 3 beeps! Once again, my MacBook Air appears to be working perfectly. Therefore, if you have recently had a MacBook Air exhibit the 3 beep boot failure, strongly consider checking your thermal paste. WARNING: You should do this ONLY you are an experienced repair person, and only if your computer is already out of warranty. FYI: I've been building, repairing and modding...