Long, long, long term test: the HD6850 did the trick and I’ve had zero graphical glitches since it went in. Have I really had my box for so many years? I just decided to order an R9 280X to replace the HD6850 to get a bit more GPU power. The 280X was chosen as it has pretty much the highest DP crunching performance of cards since both sides have taking to crippling their newer cards.
Coincidently last night I dug out 2x4GB DDR3 modules and put them in this box for 16GB total. I look at this thread and see my earlier posts about possible ram problems… maybe I should run memtest a bit longer… (passed one pass ok).
I’m actually looking up an old build thread as I’d like to try and bring some old boxes back up for crunching (heating!).