I have Scientific Linux 6.5 (2.6.32-431.11.2.el6.x86_64) installed on a Dell OptiPlex 760 with a Radeon HD 3470 graphics card and two displays hooked up to it. I'm having difficulties setting resolutions appropriate for the displays and having the two displays not show the same screen. I am not an expert in Xorg configuration and I would appreciate some assistance in getting things working.

The PCI device listing (lspci | grep VGA) for the graphics card is as follows:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV620 PRO [Radeon HD 3470]

A more detailed listing (lspci -v -s $(lspci | awk '/VGA/{print $1}')) is as follows:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV620 PRO [Radeon HD 3470] (prog-if 00 [VGA controller])
    Subsystem: Dell Device 3243
    Flags: bus master, fast devsel, latency 0, IRQ 16
    Memory at d0000000 (64-bit, prefetchable) [size=256M]
    Memory at fe9f0000 (64-bit, non-prefetchable) [size=64K]
    I/O ports at dc00 [size=256]
    Expansion ROM at fea00000 [disabled] [size=128K]
    Capabilities: [50] Power Management version 3
    Capabilities: [58] Express Legacy Endpoint, MSI 00
    Capabilities: [a0] MSI: Enable- Count=1/1 Maskable- 64bit+
    Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
    Kernel modules: radeon

The result of an xrandr query (xrandr -q) is as follows:

xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 400, current 1280 x 1024, maximum 1280 x 1024
default connected 1280x1024+0+0 0mm x 0mm
   1280x1024       0.0* 
   1152x864        0.0  
   1024x768        0.0  
   800x600         0.0  
   640x480         0.0  
   720x400         0.0

The modeline returned by the coordinated video timing utility cvt for the highest resolution capable by the main display (1680 x 1050) is as follows:

cvt 1680 1050
# 1680x1050 59.95 Hz (CVT 1.76MA) hsync: 65.29 kHz; pclk: 146.25 MHz
Modeline "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync

If I try to use this with xrandr, I get the following:

xrandr --newmode "1680x1050_60.00"  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync
xrandr: Failed to get size of gamma for output default

The entire contents of the /etc/X11/xorg.conf file is as follows:

Section "Device"
    Identifier "Videocard0"
    Driver "vesa"

I am not sure what to do next in order to get the appropriate resolutions set and to get the two displays working as two separate displays (as opposed to having the mirror behaviour).

UPDATE: I have attempted to install a driver for this graphics setup (fglrx64_p_i_c-, but have run into difficulties regarding undefined symbol noXfree86driextension. The ending contents of the file Xorg.0.log are as follows:

[    39.312] Initializing built-in extension XVideo
[    39.312] Initializing built-in extension XVideo-MotionCompensation
[    39.312] Initializing built-in extension SELinux
[    39.312] Initializing built-in extension XFree86-VidModeExtension
[    39.312] Initializing built-in extension XFree86-DGA
[    39.312] Initializing built-in extension XFree86-DRI
[    39.312] Initializing built-in extension DRI2
[    39.312] (II) "glx" will be loaded by default.
[    39.312] (II) LoadModule: "glx"
[    39.338] (II) Loading /usr/lib64/xorg/modules/extensions/libglx.so
[    39.358] (II) Module glx: vendor="Advanced Micro Devices, Inc."
[    39.358]     compiled for 6.9.0, module version = 1.0.0
[    39.365] Loading extension GLX
[    39.366] (II) LoadModule: "fglrx"
[    39.366] (II) Loading /usr/lib64/xorg/modules/drivers/fglrx_drv.so
[    39.520] (EE) Failed to load /usr/lib64/xorg/modules/drivers/fglrx_drv.so: /usr/lib64/xorg/modules/drivers/fglrx_drv.so: undefined symbol: noXFree86DRIExtension
[    39.520] (II) UnloadModule: "fglrx"
[    39.520] (II) Unloading fglrx
[    39.520] (EE) Failed to load module "fglrx" (loader failed, 7)
[    39.520] (EE) No drivers available.
[    39.520]
Fatal server error:
[    39.520] no screens found
[    39.520] (EE)
Please consult the Red Hat, Inc. support
     at https://www.redhat.com/apps/support/
 for help.
[    39.520] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[    39.520] (EE) 

1 Answer 1


AMD's proprietary driver is not supported on recent Linux Kernels like yours. It's best to get the open source radeon driver working. According to my research, the open source driver outperforms AMD's proprietary driver (a.k.a Catalyst/fglrx) and supports newer Kernel versions (read more).

I actually have the same problem. See my question here: Getting radeon driver work

  • I had far better experience on recent Linux kernels with AMD cards.
    – peterh
    Mar 13, 2018 at 16:56
  • @peterh This GPU is listed to be fully supported with the open source radeon driver. So it should work if we could get Linux to actually use this driver ...
    – xuser
    Mar 13, 2018 at 17:04
  • @peterh If your AMD graphics card is working, which Kernel do you have? Do you have a /etc/x11/xorg.conf and if so, how does this file look like on your machine?
    – xuser
    Mar 13, 2018 at 17:18
  • I tried it maybe a half year ago, with a then recent kernel. I can't remember the details. Maybe I had to download some ppa debs, too. Sorry I can't remember.
    – peterh
    Mar 13, 2018 at 17:20
  • I just found something very interesting on freebsd.org. >If you want to automatically load a video driver at boot time, we >recommend to do it from /etc/rc.conf: > >kld_list="radeonkms"
    – xuser
    Mar 13, 2018 at 17:32

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