Below two conditions :
One with /etc/X11/xorg.conf like this :
Section "Monitor"
Identifier "Monitor0"
EndSection
#Section "Device"
# Identifier "Radeon"
# Driver "ati" #Choose the driver used for this monitor
#EndSection
Section "Screen"
Identifier "Screen0" #Collapse Monitor and Device section to Screen section
Device "Radeon"
Monitor "Monitor0"
DefaultDepth 24 #Choose the depth (16||24)
SubSection "Display"
Depth 24
Modes "1280x800_59.90" #Choose the resolution
EndSubSection
EndSection
in Xorg.0.log I see :
[ 23.081] (II) LoadModule: "fbdev"
[ 23.082] (WW) Warning, couldn't open module fbdev
>:([ 23.082] (II) UnloadModule: "fbdev"
>:([ 23.082] (II) Unloading fbdev
[ 23.082] (EE) Failed to load module "fbdev" (module does not exist, 0)
[ 23.082] (II) LoadModule: "vesa"
[ 23.082] (II) Loading /usr/local/lib/xorg/modules/drivers/vesa_drv.so
[ 23.083] (II) Module vesa: vendor="X.Org Foundation"
[ 23.083] compiled for 1.19.1, module version = 2.3.4
[ 23.083] Module class: X.Org Video Driver
[ 23.083] ABI class: X.Org Video Driver, version 23.0
[ 23.083] (II) RADEON: Driver for ATI/AMD Radeon chipsets:
ATI Radeon Mobility X600 (M24), ATI FireMV 2400,
ATI Radeon Mobility X300 (M24), ATI FireGL M24 GL,
ATI Radeon X600 (RV380), ATI FireGL V3200 (RV380),
ATI Radeon IGP320 (A3), ATI Radeon IGP330/340/350 (A4),
ATI Radeon 9500, ATI Radeon 9600TX, ATI FireGL Z1, ATI Radeon 9800SE,
……..
[ 23.085] (II) modesetting: Driver for Modesetting Kernel Drivers: kms
[ 23.085] (II) VESA: driver for VESA chipsets: vesa
[ 23.085] (--) using VT number 2
[ 23.088] (II) [KMS] drm report modesetting isn't supported.
[ 23.088] (EE) open /dev/dri/card0: No such file or directory
[ 23.088] (WW) Falling back to old probe method for modesetting
[ 23.088] (EE) open /dev/dri/card0: No such file or directory
[ 23.088] (EE) Screen 0 deleted because of no matching config section.
>:([ 23.088] (II) UnloadModule: "radeon"
[ 23.088] (EE) Screen 0 deleted because of no matching config section.
>:([ 23.088] (II) UnloadModule: "modesetting"
[ 23.088] (II) Loading sub module "vbe"
[ 23.088] (II) LoadModule: "vbe"
[ 23.088] (II) Loading /usr/local/lib/xorg/modules/libvbe.so
[ 23.089] (II) Module vbe: vendor="X.Org Foundation"
[ 23.089] compiled for 1.19.3, module version = 1.1.0
[ 23.089] ABI class: X.Org Video Driver, version 23.0
[ 23.089] (II) Loading sub module "int10"
[ 23.089] (II) LoadModule: "int10"
[ 23.089] (II) Loading /usr/local/lib/xorg/modules/libint10.so
[ 23.094] (II) Module int10: vendor="X.Org Foundation"
[ 23.094] compiled for 1.19.3, module version = 1.0.0
[ 23.094] ABI class: X.Org Video Driver, version 23.0
[ 23.094] (II) VESA(0): initializing int10
[ 23.095] (II) VESA(0): Primary V_BIOS segment is: 0xc000
23.149] (II) LoadModule: "ddc"
[ 23.149] (II) Module "ddc" already built-in
[ 23.201] (II) VESA(0): VESA VBE DDC unkown failure 768
[ 23.201] (II) VESA(0): VESA VBE PanelID read successfully
:)[ 23.201] (II) VESA(0): PanelID returned panel resolution 1280x800
[ 23.201] (II) VESA(0): Searching for matching VESA mode(s):
>:([ 23.295] (II) VESA(0): Not using mode "1280x800_59.90" (no mode of this name)
[ 23.295] (II) VESA(0): Not using built-in mode "1024x768" (no mode of this name)
[ 23.295] (II) VESA(0): Not using built-in mode "1024x768" (no mode of this name)
[ 23.295] (II) VESA(0): Not using built-in mode "800x600" (no mode of this name)
[ 23.295] (II) VESA(0): Not using built-in mode "800x600" (no mode of this name)
The other with /etc/X11/xorg.conf like that :
#Section "Device"
# Identifier "Radeon"
# Driver "ati" #Choose the driver used for this monitor
#EndSection
#Section "Screen"
#Identifier "Screen0" #Collapse Monitor and Device section to Screen section
#Device "Radeon"
#Monitor "Monitor0"
#DefaultDepth 24 #Choose the depth (16||24)
#SubSection "Display"
#Depth 24
#Modes "1280x800_59.90" #Choose the resolution
#EndSubSection
#EndSection
in Xorg.0.log I see :
23.207] (II) LoadModule: "modesetting"
[ 23.207] (II) Loading /usr/local/lib/xorg/modules/drivers/modesetting_drv.so
[ 23.211] (II) Module modesetting: vendor="X.Org Foundation"
[ 23.211] compiled for 1.19.3, module version = 1.19.3
[ 23.211] Module class: X.Org Video Driver
[ 23.211] ABI class: X.Org Video Driver, version 23.0
[ 23.211] (II) LoadModule: "fbdev"
[ 23.212] (WW) Warning, couldn't open module fbdev
>:([ 23.212] (II) UnloadModule: "fbdev"
>:([ 23.212] (II) Unloading fbdev
[ 23.212] (EE) Failed to load module "fbdev" (module does not exist, 0)
[ 23.212] (II) LoadModule: "vesa"
[ 23.212] (II) Loading /usr/local/lib/xorg/modules/drivers/vesa_drv.so
[ 23.213] (II) Module vesa: vendor="X.Org Foundation"
[ 23.218] (II) [KMS] drm report modesetting isn't supported.
[ 23.218] (EE) open /dev/dri/card0: No such file or directory
[ 23.218] (WW) Falling back to old probe method for modesetting
[ 23.218] (EE) open /dev/dri/card0: No such file or directory
[ 23.218] (EE) Screen 0 deleted because of no matching config section.
>:([ 23.218] (II) UnloadModule: "radeon"
[ 23.218] (EE) Screen 0 deleted because of no matching config section.
>:([ 23.218] (II) UnloadModule: "modesetting"
[ 23.218] (II) Loading sub module "vbe"
[ 23.218] (II) LoadModule: "vbe"
[ 23.218] (II) Loading /usr/local/lib/xorg/modules/libvbe.so
[ 23.219] (II) Module vbe: vendor="X.Org Foundation"
[ 23.219] compiled for 1.19.3, module version = 1.1.0
[ 23.219] ABI class: X.Org Video Driver, version 23.0
[ 23.219] (II) Loading sub module "int10"
[ 23.219] (II) LoadModule: "int10"
[ 23.219] (II) Loading /usr/local/lib/xorg/modules/libint10.so
[ 23.224] (II) Module int10: vendor="X.Org Foundation"
[ 23.224] compiled for 1.19.3, module version = 1.0.0
[ 23.224] ABI class: X.Org Video Driver, version 23.0
[ 23.224] (II) VESA(0): initializing int10
[ 23.225] (II) VESA(0): Primary V_BIOS segment is: 0xc000
[ 23.225] (II) VESA(0): VESA BIOS detected
[ 23.279] (II) Loading sub module "ddc"
[ 23.279] (II) LoadModule: "ddc"
[ 23.279] (II) Module "ddc" already built-in
[ 23.331] (II) VESA(0): VESA VBE DDC unkown failure 768
[ 23.331] (II) VESA(0): VESA VBE PanelID read successfully
:)[ 23.331] (II) VESA(0): PanelID returned panel resolution 1280x800
[ 23.331] (II) VESA(0): Searching for matching VESA mode(s):
[ 23.331] Mode: 100 (640x400)
Warm thanks.