Nothing beats the original. It is OS independent! 

We are at a point where I still haven't had the time to investigate further.
I will

Quote from: ssp3 on Yesterday at 08:36:49 AM

G4 Mini is limited to 1920x1200 on DVI and 1920x1080 on VGA. That's about it.

VGA is working fine here with WUXGA - unlike on the stupid coreduo minis.

You're right, of course. See what happens when you carelessly quote Everymac com. Even I myself was running 1920x1200 on VGA in my ATI tests. Doh! 

My OS 9 machines (B&W G3 with G4 and PM 8600) are connected to a 5K display using a Gefen Dual Link DVI to DisplayPort adapter but they don't have GPUs that support more than 1920x1200 or 1600x1200. I do have a 7800 GT from a Quad G5 which can do 1440p60 or 4K30 but I haven't tried it in a PCI slot yet and it wouldn't have 2D or 3D acceleration in OS 9 if it could work. It would be for OS X Tiger or Leopard.

What mode is the graphics card trying to use when the display goes black?

I have no idea.

Some things to try:
- A modern display that isn't limited to 1920x1080 60Hz. I have a Acer XV273K 4K display which can accept anything up to 5K60 or 8K30 via DisplayPort. Not sure about HDMI/DVI though.

G4 Mini is limited to 1920x1200 on DVI and 1920x1080 on VGA. That's about it.

- Connect two displays - one display that is known to work so that you can see what timing is being attempted on the display that doesn't work.

There is no provision to connect two displays to G4 Mini.

- If you can't get two displays, then maybe a screen sharing app, so you can use another Mac to see what's happening when the display goes black on the first Mac.

Never used anything like that in OS9 and have no idea if such app exists.

These three are beyond the point

- A custom EDID adapter like Dr HDMI 8K.
- A scan converter that can take an input and convert it to a different timing that is acceptable by the display.
- A HDMI capture device (USB or PCIe) - maybe it can accept what ever is being output.

- SwitchRes - I don't remember if the OS 9 version has custom timing options? Maybe it can at least disable modes that don't work with your display.

It doesn't help, because computer freezes at the moment when ATI extensions load!

But, its not about my particular display, it is about latest version of ATI driver not working with ANY display.