I just recently updated some parts in my computer. I was running an AMD HD Radeon 5770 alongside an AMD HD Radeon 5450. The 5770 was my main card, and the 5450 powers two side monitors.
I upgraded the 5770 to an AMD RX 480, and am still using the AMD HD Radeon 5450. I am running Windows 8.1 64 bit. After installation, my main monitor was forced to 1920x1080, but it is an ultrawide and supports 2560x180. I went to AMD's website, downloaded the new driver, and it told me that the driver does not support the 5450 (or any of the 5XXX cards). After installation, my two side monitors do not display output, and in device manager the 5450 is displaying an error: "Windows has stopped this device because it has reported problems. (Code 43)".
I tried to install legacy drivers for the 5450, but that forced the RX 480 to display to 1920x1080 again, and the RX 480 displays the error that the 5450 was receiving.
At this point, I have now reinstalled the drivers for the RX 480, and am not using the side monitors.
Is there any way to get these two cards to work together in the same machine? The 5770 gets the same results as well. While yes, I could just use the onboard graphics or the RX 480 additional outputs, but I'd rather those monitors be on a separate device.