I have two old radeons which refuse to work as a second GPU. They are both of the same family. One x300, one x550.
I have a Radeon 290 which is my main GPU. Branded by ASUS, reference design. It is installed on a Gigabyte x99-UD4 board along with I7 5820K on Windows 10 64bit. It's great. However I occasionally need an analog output for a second screen, and 290 does not provide it. So i took x300, which does provide analog output, installed it and... got nothing. After some testing I got the following results:
- x300 works perfectly fine if installed in the slot closest to the CPU and is the only card in the system.
- x300 is invisible in the device manager if 290 is installed anywhere.
- 290 works from every slot
Testing the case further i took the x300 to my workshop and dropped it into my workstation - which is a dual Opteron 8435 on a tyan h2000 s3992e board and Windows 7 64bit. It has two pci-express slots, one of which is occupied by a Quadro 4000. I took that gpu out and installed the x300 and x550 togather. Intending to use their dvi-d outputs this time. Once again - I can get only one of those cards to show up in device manager.
TL:DR; - I can't get x550/x300 cards to work as a secondary screen.
What is the issue here? Are cards of that family incapable of being used as a secondary card?
Those old cards aren't supported by Windows 10, and they do not use the same drivers as the R9 290 so they cannot be used together. Also, why can't you use an adapter for the 290 to get VGA output?
Granted, they are not supported, but nonetheless - windows should detect a device anyways and install a default driver for it. (EDIT) That is what AMD help says, and I am fine with it (/EDIT) Besides - behavior persists on both Windows 10 and 7 and on two boards. This leads me to suspect that those cards are at fault.
290 does not provide an analog output. The best I can do is to use a converter, which I actually already ordered. Converters tho seem to have rather bad reputation, so I'd prefer a native VGA.
This issue was bothering me for some time, so I did further experiments. I tried switching those cards with NVidia NVS300 and HD7450 and, for the sake of it, an USB controller.
Both X300 and X550 fail to even boot if they are not a primary adapter and are invisible even if the first slot is taken by an USB controller. On the flip side - both 7450 and NVS can work from any slot available.
Thusly I for the sake of google robots - x300 and x550 cannot be used anywhere except for the primary PCIE slot.