Why is my external monitor’s resolution limited when running in mirror mode on a PowerBook?
Mirror mode is probably the most problematic mode to run dual displays in. When you are in mirror mode, the screen resolution has a maximum of the highest resolution available on the smaller display. In your case, that is the PowerBook’s display. Even if you had two different video cards, running each display, Mirror mode would keep the resolution capped at 1280 X 854. What many laptop owners do, when they want to use a bigger monitor without using the built-in display, is close the lid to the laptop. As soon as you plug in an external display, USB keyboard and mouse, the computer will wake up and use the full resolution of the display. Then your laptop will basically be the equivalent of a Mac mini, until you open the lid again.
