The graphics card is a (Turks Pro) Radeon HD 6570.
The default driver is installed, which apparently should be okay with AMD cards.
The second monitor is a Hanns-G HX193DPB and both monitors work on this and other Ubuntu PCs. Along with their cables.
The Hanns-G monitor is mounted at height and linked to the PC through a narrow conduit. There is a USB port and mouse with it which both work but aren't being picked up by Ubuntu.
The PC is replacing an old NVR which was also Linux-based and seemed to work better with 2x(mouse+keyboard), one mouse+keyboard inside the security cupboard and the other outside.
There are three ports with displays on two of them: HDMI is unused. VGA-0 is always okay and DVI-0 is always black. Both displays are on the same graphics card. There is also an on-board graphics card inside the PC, but it seems to be broken/physically disconnected/disabled in the BIOS - and doesn't show up anywhere.
The Ubuntu "Displays" interface shows the correct manufacturer and native resolution for the second monitor, and this can be changed with xrandr --output DVI-0 --auto. I have tried all the different mode lines shown in xrandr -q (which look correct for the device compared with its manual). The mouse can be moved off to the side of the screen when --right-of is set.
Setting DVI-0 to 640x480 50Hz causes everything on the other display VGA-0 to become garbled.
The PC is difficult to access or list outputs or logs from as it's inside a security cupboard and off the LAN.
The monitor's on-board menu has two inputs to choose from: VGA or DVI. I can't really connect to the DVI as the cable goes through a narrow conduit, but I've discounted the monitor's input detection as it can pick up the PC's VGA-0 correctly.
There are apparently bugs in this generation of cards if the VGA and HDMI outputs are connected at the same time. Is there any way I can test for this to confirm if it's the cause of the problem?
When booting up, if only DVI-0 is attached to a monitor and the other is left unplugged, the screen stays blank. Is it likely the card or the port is damaged in such a way that Ubuntu can communicate with the monitor but not display an image?
I think there would a workaround by just physically swapping the VGA from one display to the other when inside the security cupboard But I'm also having trouble connecting two mice at once to the PC, or getting Ubuntu to recognize the second mouse like the NVR's embedded OS used to do.
