I recently removed (from my S5520SC workstation) one of my dual PCI add-in graphics boards. This necessitated enabling the onboard graphics through the BIOS and cold-starting the unit to get back to a dual-screen system. However, what I encountered is that I can only get one of the two grahpics to display, regardless of which set of BIOS settings I select (onboard=enabled, dual-graphics=enabled; and all the various permutations.)
Here is the symptom: with onboard enabled in BIOS, I get VGA out of the onboard (through the ribbon connector) but the PCI graphics card (an NVidia) is blank. This happens whether the dual-graphics BIOS setting is enabled or disabled...no apparent difference.
Next, with the onboard video disabled in BIOS, I get the reverse--video out of the PCI card, but nothing from the onboard ribbon connector.
The problem is present during long, detailed POST and thereafter, so the OS is obviously a non-issue.
I suspect many things, but before I go through rigorous diagnosis, I am throwing it out to the group for "most reasonable" first steps.
[Naturally, my first steps will include ensuring I am on the latest firmwares, drivers, etc.] but also some x64 BIOS PCI memory addressing (above/below 4Gb) may be causing the conflict of displays.] Remember, too, that when there were two PCI boards installed and no onboard bideo, both PCI boards worked well together.
Well, please reply with any thoughts and useful suggestions as I move forward.
When you enable dual monitor in BIOS, the onboard video controller is enabled as the primary video device, so it will be used to display POST messages. You can extend display to your add-in graphics card after OS loads.
However if you're running Windows Server 2008 or Vista you may have a problem. Basically it's because that Windows 2008/Vista requires same WDDM driver for dual display to work. No such limitation for XPDM driver (2003/XP). See http://www.intel.com/support/motherboards/server/sb/CS-030728.htm for details.
Yep, Edward, this is invariably the problem. It is also why my homogeneous-Multimonitor support worked until I pulled one of the PCIe graphics boards out. hey were working on the identical WDDM stack. Now my onboard GA and my NVidia are on different drivers and the problem is as described in the Microsoft Technet flash: http://technet.microsoft.com/en-us/library/cc756392%28WS.10%29.aspx
Oh well. Here's what I did instead: my single PCIe NVidia card still supports multiple monitors, just through DVI and DisplayPort. So I have disabled onboard GA and am running both monitors through the single PCIe card and two differing cables.