From Fedora Project Wiki

When attempting to boot the LiveCD, X failed to start. This is the xorg.0.log from that failure. Note that X was unable to identify the primary video card, listing both of their PCI addresses.

X.Org X Server 1.6.0
Release Date: 2009-2-25
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.18-128.1.1.el5 x86_64 
Current Operating System: Linux new-host-3 2.6.29-0.279.rc8.git6.fc11.x86_64 #1 SMP Mon Mar 23 10:42:23 EDT 2009 x86_64
Build Date: 12 March 2009  01:39:13PM
Build ID: xorg-x11-server 1.6.0-13.fc11 
	Before reporting problems, check http://wiki.x.org
	to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
	(++) from command line, (!!) notice, (II) informational,
	(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Thu Mar 26 08:17:20 2009
(II) Loader magic: 0x3dc0
(II) Module ABI versions:
	X.Org ANSI C Emulation: 0.4
	X.Org Video Driver: 5.0
	X.Org XInput driver : 4.0
	X.Org Server Extension : 2.0
(II) Loader running on linux
(--) using VT number 7

(!!) More than one possible primary device found
(--) PCI: (0@3:0:0) nVidia Corporation G94 [GeForce 9600 GT] rev 161, Mem @ 0xf4000000/16777216, 0xc0000000/268435456, 0xf2000000/33554432, I/O @ 0x0000ac00/128, BIOS @ 0x????????/524288
(--) PCI: (0@5:0:0) nVidia Corporation G94 [GeForce 9600 GT] rev 161, Mem @ 0xf8000000/16777216, 0xd0000000/268435456, 0xf6000000/33554432, I/O @ 0x00008c00/128, BIOS @ 0x????????/524288
Primary device is not PCI
(==) Using default built-in configuration (21 lines)
(==) --- Start of built-in configuration ---
	Section "Device"
		Identifier	"Builtin Default vesa Device 0"
		Driver	"vesa"
	EndSection
	Section "Screen"
		Identifier	"Builtin Default vesa Screen 0"
		Device	"Builtin Default vesa Device 0"
	EndSection
	Section "Device"
		Identifier	"Builtin Default fbdev Device 0"
		Driver	"fbdev"
	EndSection
	Section "Screen"
		Identifier	"Builtin Default fbdev Screen 0"
		Device	"Builtin Default fbdev Device 0"
	EndSection
	Section "ServerLayout"
		Identifier	"Builtin Default Layout"
		Screen	"Builtin Default vesa Screen 0"
		Screen	"Builtin Default fbdev Screen 0"
	EndSection
(==) --- End of built-in configuration ---
(==) ServerLayout "Builtin Default Layout"
(**) |-->Screen "Builtin Default vesa Screen 0" (0)
(**) |   |-->Monitor "<default monitor>"
(**) |   |-->Device "Builtin Default vesa Device 0"
(==) No monitor specified for screen "Builtin Default vesa Screen 0".
	Using a default monitor configuration.
(**) |-->Screen "Builtin Default fbdev Screen 0" (1)
(**) |   |-->Monitor "<default monitor>"
(**) |   |-->Device "Builtin Default fbdev Device 0"
(==) No monitor specified for screen "Builtin Default fbdev Screen 0".
	Using a default monitor configuration.
(==) Automatically adding devices
(==) Automatically enabling devices
(==) FontPath set to:
	catalogue:/etc/X11/fontpath.d,
	built-ins
(==) ModulePath set to "/usr/lib64/xorg/modules"
(II) Cannot locate a core pointer device.
(II) Cannot locate a core keyboard device.
(II) The server relies on HAL to provide the list of input devices.
	If no devices become available, reconfigure HAL or disable AllowEmptyInput.
(II) No APM support in BIOS or kernel
(II) System resource ranges:
	[0] -1	0	0xffffffff - 0xffffffff (0x1) MX[B]
	[1] -1	0	0x000f0000 - 0x000fffff (0x10000) MX[B]
	[2] -1	0	0x000c0000 - 0x000effff (0x30000) MX[B]
	[3] -1	0	0x00000000 - 0x0009ffff (0xa0000) MX[B]
	[4] -1	0	0x0000ffff - 0x0000ffff (0x1) IX[B]
	[5] -1	0	0x00000000 - 0x00000000 (0x1) IX[B]
(II) LoadModule: "extmod"
(II) Loading /usr/lib64/xorg/modules/extensions//libextmod.so
(II) Module extmod: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension SELinux
(II) Loading extension MIT-SCREEN-SAVER
(II) Loading extension XFree86-VidModeExtension
(II) Loading extension XFree86-DGA
(II) Loading extension DPMS
(II) Loading extension XVideo
(II) Loading extension XVideo-MotionCompensation
(II) Loading extension X-Resource
(II) LoadModule: "dbe"
(II) Loading /usr/lib64/xorg/modules/extensions//libdbe.so
(II) Module dbe: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DOUBLE-BUFFER
(II) LoadModule: "glx"
(II) Loading /usr/lib64/xorg/modules/extensions//libglx.so
(II) Module glx: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	ABI class: X.Org Server Extension, version 2.0
(==) AIGLX enabled
(II) Loading extension GLX
(II) LoadModule: "record"
(II) Loading /usr/lib64/xorg/modules/extensions//librecord.so
(II) Module record: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.13.0
	Module class: X.Org Server Extension
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension RECORD
(II) LoadModule: "dri"
(II) Loading /usr/lib64/xorg/modules/extensions//libdri.so
(II) Module dri: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension XFree86-DRI
(II) LoadModule: "dri2"
(II) Loading /usr/lib64/xorg/modules/extensions//libdri2.so
(II) Module dri2: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DRI2
(II) LoadModule: "vesa"
(II) Loading /usr/lib64/xorg/modules/drivers//vesa_drv.so
(II) Module vesa: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 2.2.0
	Module class: X.Org Video Driver
	ABI class: X.Org Video Driver, version 5.0
(II) LoadModule: "fbdev"
(II) Loading /usr/lib64/xorg/modules/drivers//fbdev_drv.so
(II) Module fbdev: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 0.4.0
	ABI class: X.Org Video Driver, version 5.0
(II) VESA: driver for VESA chipsets: vesa
(II) FBDEV: driver for framebuffer: fbdev
(II) Primary Device is: 
(WW) Falling back to old probe method for vesa
(WW) Falling back to old probe method for fbdev
(II) Loading sub module "fbdevhw"
(II) LoadModule: "fbdevhw"
(II) Loading /usr/lib64/xorg/modules/linux//libfbdevhw.so
(II) Module fbdevhw: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 0.0.2
	ABI class: X.Org Video Driver, version 5.0
(II) FBDEV(0): using default device
(II) Running in FRAMEBUFFER Mode
(II) FBDEV(0): Creating default Display subsection in Screen section
	"Builtin Default fbdev Screen 0" for depth/fbbpp 24/32
(==) FBDEV(0): Depth 24, (==) framebuffer bpp 32
(==) FBDEV(0): RGB weight 888
(==) FBDEV(0): Default visual is TrueColor
(==) FBDEV(0): Using gamma correction (1.0, 1.0, 1.0)
(II) FBDEV(0): hardware: nouveaudrmfb (video memory: 9000kB)
(II) FBDEV(0): checking modes against framebuffer device...
(II) FBDEV(0): checking modes against monitor...
(--) FBDEV(0): Virtual size is 1920x1200 (pitch 1920)
(**) FBDEV(0):  Built-in mode "current"
(==) FBDEV(0): DPI set to (96, 96)
(II) Loading sub module "fb"
(II) LoadModule: "fb"
(II) Loading /usr/lib64/xorg/modules//libfb.so
(II) Module fb: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.0.0
	ABI class: X.Org ANSI C Emulation, version 0.4
(**) FBDEV(0): using shadow framebuffer
(II) Loading sub module "shadow"
(II) LoadModule: "shadow"
(II) Loading /usr/lib64/xorg/modules//libshadow.so
(II) Module shadow: vendor="X.Org Foundation"
	compiled for 1.6.0, module version = 1.1.0
	ABI class: X.Org ANSI C Emulation, version 0.4
(II) UnloadModule: "vesa"
(II) Unloading /usr/lib64/xorg/modules/drivers//vesa_drv.so
(==) Depth 24 pixmap format is 32 bpp
(EE) FBDEV(0): FBIOPUT_VSCREENINFO: Invalid argument
(EE) FBDEV(0): mode initialization failed

Fatal server error:
AddScreen/ScreenInit failed for driver 0


Please consult the The X.Org Foundation support 
	 at http://wiki.x.org
 for help. 
Please also check the log file at "/var/log/Xorg.0.log" for additional information.

I manually created the following xorg.conf file, which allowed me to start X successfully:

Section "Device"
	Identifier  "Videocard0"
	BusID       "PCI:3:0:0"
	Driver      "nouveau"
EndSection

Section "Device"
	Identifier	"Videocard1"
	BusID		"PCI:5:0:0"
	Driver		"nouveau"
EndSection