I have read that there is a problem with the current crimson driver when it comes to second life. I put together a build of an yesterday of.
AMD FX 9590
Asus Sabertooth 990FX r.2.0
Samsung Pro 500gb SSD
Toshiba 2TB HDD
32 GB Hyper Fury X
Asus Strix RX 480oc
1000 Watt Power supplier Cosair Gold Fully Modular
X61 Kracken Cooler
Window 10 Pro
Now everything else is humming along now had to do some tweaks cause of the bottlenecking issue which is now all smoothed out. Now the artifcacting is a deffinate case with the current crimson driver and there has been a lot of attempts of people trying to get their AMD cards to work this issues ranges from R series to the RX series all cards have been effected some worse than others. I get this line on the screen where its a colored line and l've seen many people with RX 480 Strix cards with the same issue.
Even now when l use my HD 7790 oc 1gb DDR5 which is running an older version of Catalyst Drivers cause in around build 15.1 the drivers were more stable as was catalyst.And it runs Second Life very well. Now l've moved to crimson on my new build l can see all the features l will be missing that could come straight from the software had crimson been any good really. No tweaking options in crimson at all its rubbish software atm. As with second life Firestorm viewer does have this problem with AMD Visual Artifacts with ALM enabled on AMD graphics and they are working on a fix from there end but AMD current crimson driver is the main problem and they are meant to be working on a driver update and fix so they have said.
https://jira.phoenixviewer.com/browse/FIRE-16829 there are a few threads about this issue not just in second life a lot of games also.
I have heard a few friends already take back their RX come home with a Nvidia and say yep no problems now. Hopefully l don't become one of them and AMD sort out the issues. And People can use second life the way they have in the past. And maybe AMD can put more of the good features later catalyst had into crimson and make it optimise the hardware as it should.Look forward to hearing about more people with this issue so it gets solved as a lot of people have written comments in the phoenix firestorm viewer bug reports and have contacted AMD about this problem.