Switching out the MSI GTX980ti for the Gigabyte GTX1080 xtreme was very easy. Both boards are the same size and use the same power connectors. I uninstalled the driver using DDU in safe mode, shut down and removed the 980 and replaced it with the 1080. I downloaded the latest driver (which I think was the same one as I already had). I haven't installed the OC Gigabyte software yet. I didn't see a lot of difference between the two boards. The 980 was already on the FI max res, but I was able to bump up MSAA from Medium to Ultra. Not much noticeable difference in terms of frame rates in the sim. Checking both CPUID and GPUID neither reported they are maxed out. My MSI 99a gaming 7 & 5820k is OC to 4.5GHz. This has been very stable for around 12 months and it never
ever crashed in XPlane 10.
Then the crashing started
Within a 30 min period of installing the card maybe 10 or so hard crashes - complete OS lockup which could only be resolved by pressing the reset button. I was pretty devastated. So the fault finding began. First remove OC on CPU. Nope. Remove all USB devices and attach a standard keyboard and mouse. Nope. Re-insert all Vive cables. Nope. In task manager, kill any unnecessary tasks. Nope. Library>Tools>Delete local content. Success. OK leave the OC off and leave off the USB devices. Start AS16, FI. Still OK. Attach Saitek Pro Yoke, TQ6, Saitek Pro pedals. Still OK. Try HyperX USB headphones still OK. Could it be the Delete Local Content. Yes absolutely. Back to OC 4.5GHz. Still OK. So my startup procedure is: Steam>Library>Tools>Delete local content>AS16>FI.
So it is now stable (mostly). I have had two occasions in the last week where the compositor(?) drops off. P3D continues to run as if nothing has happened and SteamVR is still reporting the Vive running but the headset is blue-grey. Need to investigate that one. It seemed to be when I was using the GTN750. Not sure though.
I can't say in my experience that the difference between the two cards is really obvious. I think it is the 5820k CPU that is the bottleneck. GPUID reports the 1080 running about 70%. VAS in P3D is around 1.4GB I left on hyperthreading so I might experiment with that. I am getting 54/90 with FI max settings, and P3D mostly between normal and 3/4 to the right. If I increase settings much more P3D is not as smooth - difference is quite subtle. Rather have absolutely smooth than a little stutter and higher graphics. To put that into context I was happy getting 25FPS before the Vive & FI.
If I could take the card back and get my money would I do it? No - there is a certain amount of comfort at the moment knowing that I have just about the best rig for FI and Vive.
My 2c
MSI X99A Gaming 7 MB, i7 5820K @4.5GHz, Corsair H110i GT CPU Cooler, Gigabyte GTX1080 xtreme 8GB, Corsair Veng 32GB DDR4, Samsung 850 EVO 500GB SSD, Corsair RM-750 PS Win10x64, XP11, HTCVive