Take the tour ×  We have a Mac Pro running Lion that ha no
screen attached. It is set up so it can be accessed using screen
sharing (VNC). It works with a 800 by 600 resolution.   When I
use display preferences to change the resolution while being
connected using screen sharing, this is what happens: I get a
dialog saying that if the resolution change didn't work, the
system will revert it in 15 seconds. Then the screen freezes
(nothing changes and it doesn't appear to react to clicks).
Finally after 15 seconds it reverts to 800 by 600.
share|improve this question OS X is a "little too smart" and
wants to sense out to the display to sense the resolution it
sets before the login window process starts. A DVI plug might
fool the GPU but I can't point you to one that works for sure. I
don't think anyone has posted a way to trick the resolution, but
you should have better luck than people with an attached display
since the Graphics Card on the Mac Pro is far more alterable
than a portable. –  bmike Nov 29 '12 at