I love running a 5860X1080 display setup, and I have used this for about 6 years. I did an update recently and I can No longer can get my 3-1 Eyefinity setup with an auxiliary monitor.
when I try to set up Eyefinity, I either end up with a 4-1 setup that dose not work well because of my aux monitor is a different resolution, or 3-1 with the aux monitor disabled with no display.
In the setup guide (Setting Up and Configuring Multiple Displays to Run in AMD Eyefinity Mode | AMD ) I cannot find any mention of how to setup an aux monitor or to exclude a monitor from Eyefinity. I remember on my R9 285's with CCC I was able to do this, it was as per CCC a bit clunkier than it needed it to be, but once I got it set up once I could just enable, disable, discard, start fresh, or tweek it as I chose. At somepoint most of CCC was still in Radeon Settings, because I had it set up, and now I can't get it to do what I want it to.