Power Mac 11,2 & Radeon - Disconnecting the Second Monitor

If you read the directions I provided on installing a Radeon HD graphics card and Debian 7 Wheezy on your 11,2 you probably noticed 2 monitors are required, one connected to the stock Apple/Open Firmware graphics card and another to the Radeon card.  

Why are two monitors required?  
The 11,2 uses Open Firmware.  Open Firmware was originally developed by Sun Microsystems and is also used by IBM.  When you power on your 11,2 the Open Firmware runs a basic hardware diagnostic, loads hardware drivers, and then hands control over to the OS or OS loader.  As part of the hardware diagnosis, Open Firmware will check to ensure there is an Open Firmware compatible graphics card installed, as well as a connected monitor.  If either are not present, Open Firmware will not allow the OS to load.  This is why we leave the Apple/OF card installed in the PCIe 16X slot with a connected monitor.  

After Open Firmware hands control over to the OS, the OS can use whatever devices and graphics cards are installed, it is not limited to using only Open Firmware devices.  This is how we can use PC graphics cards with Linux on our 11,2 systems, and is the reason why the system starts the boot up process on the monitor connected to the Apple/OF card, and switches to the monitor connected to the Radeon card after the OS takes over and loads the radeon driver.  

Can the monitor be disconnected from the stock Apple/OF card?  
Two monitors are required during installation and configuration of the OS and radeon driver.  After this has been successfully completed, it is possible to configure Open Firmware to allow the system to boot up without a monitor attached to the stock Apple/OF graphics card.  If you choose to do this, your screen will simply remain blank until the OS loads the radeon driver.  

Can the stock Apple/OF graphics card be removed?  Wouldn't the Radeon provide better performance in the 16X slot?  
Open Firmware can be configured to allow the system to boot without an Open Firmware graphics card installed.  However, the system will be highly unstable and hardware faults will cause the system to completely lockup.  I believe this is related to the HyperTransport interconnection system used in our 11,2 systems.  So, we need to leave the stock card installed in the PCIe 16X slot.  PCIe 8X provides more than enough bandwidth for a graphics card running in 1080P without hitting a bottleneck.  It isn't until 4k that 16X starts showing (very) modest performance gains compared to 8X.  

Before disconnecting the monitor from the stock Apple/OF card...
Keep in mind that if you ever need to boot from CD or boot into OF, you will need a monitor connected to the stock Apple/OF card.  Also, if there are any errors that occur before the OS loads the radeon driver you would have no way of knowing.  However, if you suspected a problem or needed to boot from CD you could always reconnect a monitor to the Apple/OF card.  

How to configure Open Firmware to boot the system without the Apple/OF card... 
1)    Begin with your 11,2 powered off.  
2)    Power on the system.  Immediately after the startup chime, press and hold CTRL + ALT + O + F (command + option + O + F).  
3)    The system will boot into the Open Firmware console; type:  
 setenv boot-device hd:2,yaboot and press enter.  
4)    Type reboot and press enter.  

If you ever need to reset Open Firmware to factory default settings...

1)    Begin with the system powered off.  
2)    Power on the system.  Immediately after the startup chime, press and hold CTRL + ALT + R + P (command + option + R + P).