External monitor not going full resolution on extended desktop

So when running in extended mode, if you go into Displays preferences, are you saying 1680 x 1050 is not there for you to choose as an option? Was it ever there before and only recently it stopped working? Just curious.

Hmm, strange problem, but it could be a result of OS X's preference files for displays being corrupted. You have nothing to lose by trying the following procedure.

In /Library/Preferences is a file called com.apple.windowserver.plist. Navigate your way to it and throw it in the trash. Also, in your main user account (folder with your name on it) under ~/Library/Preferences/ByHost will also be found a file com.apple.windowserver.xxxxxxxxxx.plist where the xxxxx is a string of letters and numbers. Throw that file in the trash, too. Now restart.

When OS X restarts and finds those files missing from their expected location, it creates fresh copies with default values. This will give a clean start with any attached display and hopefully get things working the way they should.

I believe if the the monitor goes blank while using the Macbook it means that the MB does not support the resolution. One other alternative, and this is a weird one, is that most Apple products works great with other Apple products but not with "Outsiders"....you may want to re-consider buying a Apple cinema display if it bothers you that much.

I am having the same issue with my aluminum Macbook and my 30" Apple cinema display. It only allows me to go up to the Macbook screen resolution. I have tried dumping the prefs, and mirroring is NOT on. I have tried restarting, zapping pram, prayer and shooting REALLY dirty looks at the ichat camera... nothing is working.

Any other ideas are welcomed!

You'll need this in order to drive a 30" ACD to full resolution from an Aluminum MacBook:

http://store.apple.com/us/product/MB571Z/A

shmootz, the issue your computer is having is pretty unusual. Proof that everything is working as it should lies in the fact that, in lid-closed operation, the monitor runs at full, 1680 x 1050 resolution. That means there is no problem with the hardware or interface (VGA in this case) in my mind. Why it only gets to 1600 x 1000 when running in extended screen mode has me baffled. Especially given that it does show up as a choice in extended mode, but results in a black screen.

You could try switching to DVI to see if the problem goes away. One more thing that occurs to me...in both closed-lid and extended mode, when 1680 x 1050 is chosen, are both set to 60Hz? Maybe the 1680 x 1050 refresh setting in extended mode has been set too high, like 75Hz or higher. That's something to check. It should be 60 Hz in all cases.

There is a clue here in what might be going on. Note that the MacBook's 1280x800 display is a 16:10 aspect ratio (exactly). Now, the external resolution that is reported by shmootz is 1600x1000 which is also a 16:10 ratio. It looks to me that the system is running as if it is in the mirrored mode. The video driver will force the displays to the same aspect ratio when running as mirrored displays.

I'd try a few things to see if you can reset the display options. First, try toggling the "Mirror Displays" option in System Preferences -> Displays -> Arrangement. Second, you may want to try a reset of your PRAM and the SMC.

Here is a link to Apple's support article on resetting the PRAM:

http://support.apple.com/kb/HT1379

Here is a link to Apple's support article on resetting the SMC:

http://support.apple.com/kb/HT1411

shmootz wrote:
Thanks for your help so far ... looks like I am going to have to take it to the Apple store even though it's no longer under warranty :s

Why is it no longer under warranty? The Aluminum MacBooks haven't even been out for a year (they were introduced on Oct. 14, 2008 which means that you should have 4 months or more remaining on your one year warranty).