我购买了第二张 radeon 双头卡，这样我就可以拥有 3 个显示器。我正在运行 kubuntu，通常，我只是打开系统设置并管理显示器。我的新卡/显示器没有出现在该界面中，但是一些系统的一部分可以看到它们。我目前不是有一个xorg.conf文件，因为之前对我来说这总是“有效”。
$ lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos XT [Radeon HD 7470/8470 / R5 235/310 OEM]
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos XT [Radeon HD 7470/8470 / R5 235/310 OEM]
# lshw -c video
*-display
description: VGA compatible controller
product: Caicos XT [Radeon HD 7470/8470 / R5 235/310 OEM]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:01:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=radeon latency=0
resources: irq:28 memory:e0000000-efffffff memory:f7e20000-f7e3ffff ioport:e000(size=256) memory:f7e00000-f7e1ffff
*-display
description: VGA compatible controller
product: Caicos XT [Radeon HD 7470/8470 / R5 235/310 OEM]
vendor: Advanced Micro Devices, Inc. [AMD/ATI]
physical id: 0
bus info: pci@0000:03:00.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
configuration: driver=radeon latency=0
resources: irq:30 memory:d0000000-dfffffff memory:f7d20000-f7d3ffff ioport:d000(size=256) memory:f7d00000-f7d1ffff
一些有趣的部分/var/log/Xorg.0.log：
[ 4.752] (==) Log file: "/var/log/Xorg.0.log", Time: Tue Jan 24 17:00:38 2017
[ 4.754] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[ 4.767] (==) No Layout section. Using the first Screen section.
[ 4.767] (==) No screen section available. Using defaults.
[ 4.767] (**) |-->Screen "Default Screen Section" (0)
[ 4.767] (**) | |-->Monitor "<default monitor>"
[ 4.768] (==) No monitor specified for screen "Default Screen Section".
Using a default monitor configuration.
[ 4.768] (==) Automatically adding devices
[ 4.768] (==) Automatically enabling devices
[ 4.768] (==) Automatically adding GPU devices
...snip...
[ 4.779] (II) xfree86: Adding drm device (/dev/dri/card0)
[ 4.779] (II) xfree86: Adding drm device (/dev/dri/card1)
[ 4.779] (EE) /dev/dri/card1: failed to set DRM interface version 1.4: Permission denied
[ 4.779] (II) config/udev: Ignoring already known drm device (/dev/dri/card1)
[ 4.780] (--) PCI:*(0:1:0:0) 1002:6778:1028:2120 rev 0, Mem @ 0xe0000000/268435456, 0xf7e20000/131072, I/O @ 0x0000e000/256, BIOS @ 0x????????/131072
[ 4.780] (--) PCI: (0:3:0:0) 1002:6778:1028:2120 rev 0, Mem @ 0xd0000000/268435456, 0xf7d20000/131072, I/O @ 0x0000d000/256, BIOS @ 0x????????/131072
如果我设置了一个xorg.conf包含以下内容的：
Section "Device"
Identifier "First"
Driver "radeon"
BusID "PCI:1:0:0"
EndSection
Section "Device"
Identifier "Second"
Driver "radeon"
BusID "PCI:3:0:0"
EndSection
看起来Xorg.0.log像：
[ 4.186] (==) Log file: "/var/log/Xorg.0.log", Time: Tue Jan 24 17:11:22 2017
[ 4.188] (==) Using config file: "/etc/X11/xorg.conf"
[ 4.188] (==) Using system config directory "/usr/share/X11/xorg.conf.d"
[ 4.196] (==) No Layout section. Using the first Screen section.
[ 4.196] (==) No screen section available. Using defaults.
[ 4.196] (**) |-->Screen "Default Screen Section" (0)
[ 4.196] (**) | |-->Monitor "<default monitor>"
[ 4.198] (==) No device specified for screen "Default Screen Section".
Using the first device section listed.
[ 4.198] (**) | |-->Device "First"
[ 4.198] (**) | |-->GPUDevice "Second"
[ 4.198] (==) No monitor specified for screen "Default Screen Section".
Using a default monitor configuration.
[ 4.198] (==) Automatically adding devices
[ 4.198] (==) Automatically enabling devices
[ 4.198] (==) Automatically adding GPU devices
这让我觉得它试图将第二张视频卡用作第一张视频卡的某种渲染助手？另外，我不确定permission deniedDRM 行中的内容到底是什么 - 谷歌搜索没有找到太多帮助。新显示器做屏幕kubuntu变黑（那是启动帧缓冲区还是别的什么？不确定那是什么……）
如果有帮助的话，我很乐意附上完整的Xorg.0.log文件，或者dmesg，或者其他什么。
如果您读完了这篇文章，我在此先表示衷心的感谢。
答案1
我不是 Radeon 用户，但我认为多卡设置不适用于开源驱动程序https://www.x.org/wiki/RadeonFeature/
尝试二进制驱动程序：https://help.ubuntu.com/community/BinaryDriverHowto/AMD