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    SubjectRe: Dual Monitor
    Derrik Pates <dpates@cavern.nmsu.edu> writes:

    >If you have a PCI-based system, 2 (S)VGA cards is not a problem.

    It has at least the following problems:

    1. You've got to initialize all the VGAs you want to use. On system
    startup only one VGA gets initialized, and the code that does the job
    is in the VGA BIOS. All other VGAs are disabled. Initializing a VGA
    is chip-specific and non-trivial. I have worked in the graphics
    industry quite a while and have seen some fantastically complex
    initialization schemes necessary to get various chips to the point
    where their VGA subset can be used. Chipset specific code is not a
    problem for something like an X server that is already chipset
    specific, but it's not something you will find a generic solution to.

    2. If you are using the VGA I/O registers (0x3C4, etc.) and memory
    ranges (0xA0000, etc.), you will only be able to access one chip
    at a time.

    3. Assuming point 2 is not a problem, you still have to manage to get
    the VGA I/O and memory accesses forwarded to the PCI bus that the VGA
    you are currently using is located on. You can't assume all the VGAs
    are on the same bus.

    I've had to deal with these problems, so I know what I'm talking
    about.


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