I have a Radeon PCI card powering my 2nd monitor. Actually, it powers my main monitor, but technically itis the 2nd monitor because #1 is controlled by the AGP Rage 128 card. I was having problems getting that card to work with OS X until I stumbled on something that seems to work for me.
My Setup
500 MHz Power Mac G4 (Sawtooth)
768 MB RAM
AGP Rage 128 Pro
Radeon PCI card (32 MB)
The Symptoms
Starting my Mac in Mac OS X with two monitors powered by the two video cards results in only the AGP Rage 128 Pro powered monitor working. The Radeon PCI powered monitor eventually turns on, but remains a washed out light grey color, and the desktop is not visible. The computer finishes starting up and seems to consider there to be two monitors in operation. The computer is extremely sluggish (unusable) and crashes within few minutes. Opening up the System Prefs is not possible. Most apps wonit launch.
The Solution
Turn off your Mac. Make sure that both monitors are connected to two video cards, but turn the Radeon PCI powered monitor off. Leave your other monitor on. Start up your Mac in Mac OS X. Wait for the opening startup to proceed as normal. You should see the small Mac in your AGP monitor. That screen should eventually become the blue startup screen. Wait until your hard drive is noticeably cranking away and then turn on your Radeon PCI powered monitor. You should get the same blue screen, and depending on where you set you menubar to show in your Display Prefs (in the System Prefs), you will eventually get the login screen in one monitor or the other, but both monitors should work fine. If you have your AGP card powering your main monitor, you may just want to wait until you see the login window before turning on your other monitor.
I have absolutely no idea why this should work, and I only stumbled across it by accident.
Exceptions
There have been a couple of times when even this method did not work, and I found it necessary to try up to three times before it worked. But it has worked every time (eventually), and numerous attempts booting up the normal way (both monitors turned on during the entire process) has never ever worked for me with the Radeon PCI card.
The Voodoo 3
This "method" happens to be the same method that allowed me to use a Voodoo 3 card with Public Beta, and I am guessing that it will work with the final release for those having trouble with that unsupported card. Note that the Voodoo 3 was completely un-accelerated and was really only useful to power a second monitor (for palettes and such). The Radeon PCI card, on the other hand, is either accelerated (2D and QuickTime), or is fast enough that I simply have not noticed the same slowdown I saw with the Voodoo 3 card. I have not had time to test this, but I wanted to get this out for those looking for help with this. Again, I would like to stress that I donit know why this worked for me. :-)
Post your comments below, or add to our thread on this subject in the Mac OS X forums. I am especially interested in hearing from people who have tried this (whether or not it worked!), or found other work-arounds.