Resetting Screen Resolution at Startup

 
 
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BigMac
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Posted: 23 September 2006 04:52 PM

I have a G4 Dual 450 Running Panther that I hooked up to a small 21” HD Flat Screen TV through VGA to VGA cable. It worked fine but then I went ahead and started fiddling with the screen resolution settings and set it to something the TV cant handle. I got a screen on the tv saying “uncompatible format” but I can’t figure out how to switch it back without plugging it into another monitor (which I don’t have). I tried restarting and that didnt work.

I just installed the OS so I have nothing on it yet. Is there a keystroke to reset back to factory settings?

     
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Buzz Bumble
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Posted: 23 September 2006 11:35 PM

I’m not sure what Mac OS X does, but in the good ol’ days of the proper Mac OS when switching the screen resolution the Control Panel used to pause in the new setting with an OK / Cancel window and if you didn’t reply within a few seconds (or clicked Cancel) it simply switched back to the original setting.

If Mac OS X is the same and you’ve clicked OK or some sort of equivalent, then you could be stuck.

Simply re-booting won’t fix it since the setting is now saved. A couple of things to try:
- resetting the PRAM
- boot from the Mac OS X install CD / DVD (and probably re-install the OS)

Depending on the setting you used, finding a monitor that can handle it might be difficult.

     
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Frozonecold
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Posted: 24 September 2006 02:14 AM
BigMac - Sep 23, 2006 04:52pm

I have a G4 Dual 450 Running Panther that I hooked up to a small 21” HD Flat Screen TV through VGA to VGA cable. It worked fine but then I went ahead and started fiddling with the screen resolution settings and set it to something the TV cant handle. I got a screen on the tv saying “uncompatible format” but I can’t figure out how to switch it back without plugging it into another monitor (which I don’t have). I tried restarting and that didnt work.

I just installed the OS so I have nothing on it yet. Is there a keystroke to reset back to factory settings?

Okay you have to reset the pram by, pressing Command-Option-P-R at startup until you hear the startup chime twice, that should reset the screen resolution. But to what it resets to, I don’t know.

     
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BigMac
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Posted: 24 September 2006 11:06 AM

Ok. I reset the PRAM and that did not work. I then located a monitor and was able to change the resolution mode on the computer, save it and then switch the cables to the TV. The screen then worked, but when I restarted the computer it reverted back to “Cannot display this video mode”

Is thios a TV issue perhaps? Or is this a computer issue?

     
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Frozonecold
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Posted: 24 September 2006 11:33 AM
BigMac - Sep 24, 2006 11:06am

Ok. I reset the PRAM and that did not work. I then located a monitor and was able to change the resolution mode on the computer, save it and then switch the cables to the TV. The screen then worked, but when I restarted the computer it reverted back to “Cannot display this video mode”

Is thios a TV issue perhaps? Or is this a computer issue?

I think it may be a tv issue, keep the Mac connected to the monitor and restart, so you can see if the resolution reset itself. The pram method might not have worked, because whatever resolution, it reset to was too high. BTW: What resolution, did you set the Mac to, for the tv?

     
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BigMac
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Posted: 24 September 2006 01:38 PM

I restarted and it gave me the same issue. I had set the resolution to the lowest possible: 640 X 480

     
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Frozonecold
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Posted: 24 September 2006 02:32 PM
BigMac - Sep 24, 2006 01:38pm

I restarted and it gave me the same issue. I had set the resolution to the lowest possible: 640 X 480

Did you restart with the monitor attached, and check to see that the resolution did not revert.
     
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Buzz Bumble
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Posted: 25 September 2006 03:14 AM

Just a guess, but ...

The Mac could be starting up in a higher resolution, I know mine starts up in a lower one then flicks to the one I’ve set in teh Control Panels (Mac OS 9). Under Mac OS X the machine could be waiting in the higher resolution for you to enter your login password / select a user.

Maybe try using the monitor to set the resolution you want and turning off the ‘login user’ option when starting up so that the computer automicatall logs-in, keeps going and boots up to the Desktop. That way it should load in the appropriate resolution setting.

     
waywardtech
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Posted: 25 September 2006 05:21 PM

The only way I’ve been able to fix this issue reliably is by using a different display to do a clean restart & shutdown.

If you then plug your system back into the HD display, it should startup at a safe resolution.

     
jeofredo
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Posted: 25 September 2006 09:07 PM

Hmm… Have you tried Detect Display in System preferences after switching the cables from the monitor to the TV, but before rebooting?  It should detect which resolutions it can/can’t display and keep the resolution inside those parameters even after rebooting.

     
John Lockwood
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Posted: 26 September 2006 06:19 AM

Many TVs especially the new flat screen LCD/Plasmas, do not correctly report resolutions to a computer via DVI/HDMI connections, usually VGA connections are less problematic.

For these problematic TVs additional software such as DisplayConfig X or SwitchRes X can help.
See http://www.3dexpress.de/ for DisplayConfig X and http://www.switchres.info for SwitchRes X.

I have also seen that older Macs with older video cards are less capable than newer Macs in terms of variety of resolutions supported.

However the above is more likely to apply to DVI rather than VGA.

Another suggestion for all instances (DVI, VGA, Mac, PC) is to set up the computer so it can be remotely controlled by another computer, this could be via VNC, Apple Remote Desktop, Timbuktu, or if you are using Windows XP (you are obviously not) Microsoft Remote Desktop. By remotely controlling the computer, you can change resolutions even if the display itself is not working. I used this approach myself for example when experimenting trying to get the best results connecting a Mac mini to a Sony 40” LCD HDTV via DVI.