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Re: Using a second display adapter

Digby Tarvin wrote:
I am thinkng of adding a second display adapter to experiment with. I'm not
really interested in dual head X (I'd use single dual head
adapter for that). I am more interested in having some display hardware that I can experiment with without effecting my console/X display.

Can anyone explain what happens hardware wise when a second adapter is
present? For example, adding a PCI adapter to a system that already
has an AGP card.

Just put the second one in xorg. conf:

Section "ServerLayout"                                          #[her]
        Identifier      "X0"
        Screen      0   "Screen X0"     0 0
        InputDevice     "Mouse0"        "CorePointer"
        InputDevice     "Keyboard0"     "CoreKeyboard"

Section "ServerLayout"                                          #[me]
        Identifier      "X1"
        Screen      0   "Screen X1"     0 0
        InputDevice     "Mouse1"        "CorePointer"
        InputDevice     "Keyboard1"     "CoreKeyboard"


Section "Device"
        Option      "AllowGLXWithComposite"     "On"
        Option      "RenderAccel"               "True"

        Option      "NvAGP"                     "0"
        Identifier  "nvidia0"
        Driver      "nvidia"
        VendorName  "NVidia"
        BoardName   "GeForce4 MX 4000 AGP 8x"
        BusID       "PCI:1:0:0"

Section "Device"
        Option      "AllowGLXWithComposite"     "On"
        Option      "RenderAccel"               "True"
        Option      "RandRRotation"             "1"
        Option      "NvAGP"                     "0"

        Identifier  "nvidia1"
        Driver      "nvidia"
        VendorName  "NVidia"
        BoardName   "GeForce4 MX 440 AGP 8x"
        BusID       "PCI:0:10:0"


and in /etc/gdm/gdm.conf:

# Definition of the standard X server.
name=Standard server
command=/usr/bin/X1 :0 -layout X1 -dpi 110 -deferglyphs 16 -isolateDevice \"PCI:0:10:0\" vt7
# Definition of the second X server.
name=2nd server
command=/usr/bin/X0 :1 -layout X0 -dpi 110 -deferglyphs 16 -isolateDevice \"PCI:1:0:0\" -sharevts

I assume that video memory for more advanced modes will be mapped to unique addresses by the PCI magic, but arn't the legacy modes like
CGA etc tied down to fixed addresses (eg SVGA tex mode to segment b000h)?
Is it possible to have have two text mode displays simultaneously?

No. Video of the Linux console is rather primitive. Only the first adapter has the VT's.

As soon as X dies you lose the other monitors/keyboards/mice.


The sort of thing I would like to experiment with is having a 'diagnostic'
screen which the kernel can write a message to in real time by just
writing ascii to a memory address.

Perhaps it is something I can do without a custom driver using the
framebuffer interface? Except I don't necessarily want the complexity/
overheads of rendering fonts. Can I have a text mode frame buffer?

Anyway, the current adapter in this system is a AGP nVidia:
01:00.0 VGA compatible controller: nVidia Corporation NV25 [GeForce4 Ti 4200] (rev a3) (prog-if 00 [VGA])
        Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 137
        Memory at fd000000 (32-bit, non-prefetchable) [size=16M]
        Memory at f0000000 (32-bit, prefetchable) [size=64M]
        Memory at f4880000 (32-bit, prefetchable) [size=512K]
        Expansion ROM at feae0000 [disabled] [size=128K]
        Capabilities: [60] Power Management version 2
        Capabilities: [44] AGP version 2.0

Any reccomendations on a goood card adapter to look for for this? The main
thing is probably a clean and simple hardware interface, and good open
source friendly documentation for driver writers. Doesn't need to be
state of the art - Something I can find cheaply on eBay (along with a
1280x1024 LCD display) would probably suffice.

I only use Nvidia. Best cards best support although proprietary driver.

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