However, OSX should be able to do this on its own. This will clear out the processes that might be stuck in your memory. Open terminal, type into terminal, 'sudo purge', and then it will ask you to enter your admin password. It might be helpful to try a purge of your memory in case the OSX is having problems handling the off market memory modules. powering down the computer from laptop display.disconnecting the mini display cable from the mac.opening the laptop while still attached to monitor.The computer still thinks it is attached to screen and when I try to power up from the laptop display the computer does not know how to start. Its something to do with the mac handling of the memory when attached to a different display, and then trying to power up the computer without the display attached anymore. The only way to fix this is to open computer and remove memory modules and then reboot. I have found that when I have mac hooked to monitor and either sleep or shut down while it is connected to the monitor and unhook it and try to power it up I will get the beeps. I also have my computer hooked up to a monitor through the mini display port.

I have a mid 2012 macbook pro with i5 and integrated graphics.

The memory worked fine for a while but then I had it happen again to me last week. I have experienced a similar problem and sent my memory modules back in to crucial to get replaced.

Macbook pro 3 beeps apple logo