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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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