Late-2008 MacBooks: Image problems on external displays with mini-DisplayPort converters

The new MacBooks and MacBook Pros come with a Mini-DisplayPort adaptor for external video, and Apple supplies various adaptors (DP to DVI, and DP to VGA) to accommodate current monitors. Some users are having difficulties with their adaptors when connected to certain monitors.

Apple Discussions poster Ocell writes:

"I have the exact same problem with my Viewsonic VG2030wm 20" LCD. I've ruled out bad DVI cables. The Macbook Pro works with my 12" Cintiq's display, and the Viewsonic works with my Intel iMac, so the video out/mini displayport adaptor/dvi cable/viewsonic display are all operational. It's just the specific combination of the Macbook Pro and Viewsonic that doesn't work."

This problem has been found to frequently occur with DVI adaptors attached to their computers, however it has also happened with users connecting to the VGA adaptors. In these cases, unlike the DVI situation where no signal gets through, users have noticed the screen blinking or shutting off at random times. While drivers may definitely be suspect, the problem appears to be hardware-related since users have experienced the issue both in Mac OS X as well as in Windows via Boot Camp.

The DisplayPort connections used on the new MacBooks have slight differences in their protocols than other connection types, which allows for expanded functions in smaller connectors, but also can run users into difficulties, especially when older connetion types are used. While there could be software involvement in this problem, it sounds like there's most likely a firmware-related problem that hopefully can be patched by Apple, or at least be accommodated for in a driver update.

Things to Try

Reset the monitor to defaults If there is a method for fully resetting the monitor, try doing that first. Most have a menu option to reset to factory defaults, but in addition there may be a way to fully reset the device such as unplugging it for an extended period of time. This information may be available on the manufacturer's website, or users can just try unplugging the device for an extended period such as 20-30 minutes.

Toggle various monitor setups In the "Displays" system preferences, toggle desktop mirroring on and off to see if the monitor is not just extending the desktop to the second monitor. Especially if users have black wallpaper on their desktops, secondary monitors that are just serving as extended desktops may appear to be off when connected. Alternatively users can try dragging documents off the sides of their main monitor to see if they go over to the second monitor.

Reset the computer Users might try resetting the computer's PRAM (which does contain some graphics parameters) by holding the options, command, P, and R keys down at bootup until the computer resets and makes the boot chimes again. Release the keys and allow the computer to boot normally. Additionally, users might try resetting the computer's system management controller. Here is an Apple Support article on how to do that.

Use a different monitor Unfortunately, with hardware problems such as this users will not be able to do much, so if another monitor is available that works then users should switch to that.

Try another adaptor Many monitors support both VGA and DVI inputs, and there is potential for users to get things working by using another connection type. Additionally, while it may be a long shot, users might also try chaining together various adaptors. For instance, users might try going from displayport to DVI, and then using a DVI to VGA adaptor as the next connection, to see if that somehow sends a proper signal to the monitor.

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