MacFixIt reader Erik has posted a detailed description of his experience with trying to get a new LaCie flat-panel display (connected via DVI) working with an older ATI Radeon card, finding in the end that the older card was not capable of driving higher resolutions on the new display.
"I installed the brand new LaCie photon20vision on the G4/450DP with the original Radeon 2X AGP using the DVI cable. The screen would stay black all the time. I suspected a problem with the connector, so I tried the screen with the VGA cable, and everything was fine. What made me suspicious was that whenever I switched back to DVI, the screen would go black and then the Power Saving Warning box would appear.
"I then tried an original Rage Pro in the G4/450DP. As this card had never been used with Mac OS X, I guessed there wouldn't be any settings left in memory[...]. I was right. The screen came up beautifully in 640 x 480 resolution."
Erik's only option was to buy a new Radeon 9000 Pro display.
Solution for screen going black However, Erik's troubleshooting experience did reap a valuable tip for users who are getting a black screen when attempting to use a newer DVI flat panel with their graphics card.
"I ran into another problem due to this lacking feature: whenever I would accidentally switch resolutions using the display icon in the menu bar, the screen would go black again, because the lower resolutions Apple offers have refresh rates that are beyond the LaCie's capabilities.
"I found that I could make the screen work again, nevertheless. This is what I did: when the screen would go black, I would restart the machine using the keyboard shortcut [Ed.- on some Macs there is only a manual reset button] -- I don't have to see what I'm doing there, and if it takes longer than expected, I just hit the Return key to make dialogues go away if that is what is keeping the logout process busy. I would then start up in single-user mode and remove the /Library/Preferences/com.apple.windowserver.plist file. This file is only created after you change your display settings. Removing it, clears the settings and starts up the computer using a resolution and refresh rate that is suitable for your screen."
UPDATE: MacFixIt reader Jonathan Duke reports that conversely, some newer ATI Radeon cards cannot be used with some older DVI displays.
"Like Erik, I've got a problem, however mine is reversed. I have an "old" (2001 vintage) IBM T85D LCD with only a DVI connection. At the moment, the only video card I've found that works with it is the Apple/ATI Rage 128 Pro with an ADC connector. The newer ATI Radeon 9000 that ships with the current G4 systems won't work with this display."