ATI Radeon X1900 XT 512 MB graphics card has failed?

Question

I think my ATI Radeon X1900 XT 512 MB graphics card has failed...
This is a MacPro 1,1 (2006). We're on our yacht in a French territory, South Pacific, so local support is non-obtainium. I would appreciate any advice on how I can confirm my graphics card is dead.
I have only 23" Apple Cinema Display for testing. The display works great on MBP, so that end is good.
The MacPro seems to boot normally - AFAIK based on startup sounds, fan, RAM LED diagnostic lights.
Suggestions?

Answer 1

Case A) the screen goes blank at the login screen
invoke Safe Mode (hold down the Shift key at Startup).
This performs a five minutes or so Disk Utility ( Repair Disk) on the boot drive, then demands your userId and password, even if you normally auto-login.
Safe Mode only loads the absolutely essential Drivers, and the graphics drivers are not considered essential. So screen re-draw may be slow, but you can check your email, surf a little, do many operations that do not require graphics acceleration.
Edit movies? Probably not.
Case B) your screen completely blank
If the power-on light flashes in a pattern, that indicates not enough good RAM to start up.
If no power light flashing, you need some function you can invoke that will show a non-graphics result.
The Caps Lock light on the keyboard is under software Control. If it works, at least the SMC controller that talks to the keyboard is working.
Holding down Control while pressing the Eject key on the keyboard brings up this familiar dialog box, whether you can see it or not:
any key except:
R for Restart;
S for Sleep;
Esc for cancel;
and return for the default Shut Down
should cause the System Beep sound. S should Sleep it, and the power light should shortly indicate that it is sleeping. Any key will then wake it up.