In Snow Leopoard and earlier, you could open the lid of your laptop after you had activated clam shell mode and the display would remain inactive until you disconnected the external monitors.

In Mountain Lion (and Lion?), the behavior is to immediately turn the display on.

My question is, is it possible to restore the earlier behavior?

Note that none of the solutions listed here actually restore this behavior. The boot-args option is especially egregious as it disables the internal display completely until you reboot. This is far less than desirable.

If you need more detail about the specifics of the Pre-Lion behavior, leave a comment.


You can get pre-lion behavior with:

sudo nvram boot-args="iog=0x0"

  If it screws up your system, just zap the PRAM next boot (cmd+opt+p+r) and you'll be back to the default state.

Or from terminal, this command will get you back to Lion's default state as well:  

sudo nvram -d boot-args
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  • See the question. I note especially that modifying the boot-args is not a solution to this, and completely does not restore the pre-lion behavior as it simply disables the internal display completely until you reboot. Unless my understanding is off. – Tim Visher Jul 12 '13 at 13:03

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