I have a 980TI and from doing lots of reading there appears to be issues with this card and Windows 10.
Sergey from BF recently made an addition to this ticket on the Blender bug tracking system.
It seems he has come to the conclusion that the issue is/most likely is an issue with Windows 10 and or the NVidia Drivers.
If this is where the issue lies what do we do next? Windows 10 is heading towards its first anniversary and the card itself isn’t particularly new either. How can we push for a fix or other help from MS/NVidia?
I was wondering if anyone had seen anything similar already reported to them. Would be good to add to that rather than lots of people starting individual complaints.
The first issue seems to be related to Windows 10/Nvidia drivers for the 980Ti and Titan X and results in poor performance of these cards on windows 10 machines compared to Linux.
The second issue seems to be to do with Blender 2.77 itself which took a huge hit in performance over 2.76.
For the first issue - I guess we need to get onto Nvidia/Microsoft to see if they can offer a fix - however for the Blender issue, there is some testing we can do to help the devs. Something must have changed between 2.76 and 2.77 - and it would be interesting to see how card/OS specific it is.
I have run some speed tests using my Windows 10 / GGTX 980Ti machine over several blender versions from 2.73 up to 2.77.
These results show a sharp reduction in rendering speed between 2.76 and 2.77.
It would be interesting to see if people on other operating systems with other graphics cards (particularly Nvidia cards) see a similar decrease in performance between 2.73 and 2.77. I have an old machine running Windows 8 that I don’t use anymore - but I may fire up later for some testing. I may also pull the graphics card out of it and stick it in my windows 10 machine to see how it compares to my 980Ti.
Basically - the GTX 480 is only slightly slower than the 980Ti under Win 10 and V2.77 - and shows no slow down when going from from 2.76 to 2.77. The slow down from 2.73 to 2.76 is also much less.
I might now move the GTX 480 to my Windows 10 machine and see what happens.
Around 2% faster than the 480 results posted by the Windows 7 machine.
I then tried rendering the scene with both the 980Ti and 480 running together. Results are pretty much as expected with the 980Ti taking up the slack under version 2.73 and 2.76 - but only just keeping up with the GTX480 under 2.77.
Interestingly in this test 2.76 performed the worst - with 2.73 and 2.77 posting almost identical render times. After installing the graphics card on this old machine - I updated to the newest Nvidia drivers 365.19 before running the test.
The 980Ti renders slightly slower on the Windows 7 machine compared to the Windows 10 machine for blender 2.73 - but 2.76 and 2.77 are much faster on the Windows 7 machine.
I used to have 3 GTX 580 3GB cards, I’ve sold them to a blender artists. But before I did I wrote down my render times. So this is for the BMW27 scene by Mike Pan (latest benchmark file, two BMWs)
2x GTX 580 3GB, Win 8 64bit, CPU i7 3820 1m11s
With my new system, rendering the very same scene.
2x Titan X 12GB, Win 10 64bit, CPU i7 3820 1m35s
Brecht had been in touch with nvidia and they asked to upgrade to latests driver so I’m on 365.19.
So something is off, and Sergey seems to have tried everything with the 980Ti they got delivered to the foundation by some user. Would be nice to know if it’s Operating System issue, driver issue? or combination, or even those compiled files, SM_ kernels that needs to be recompiled after updates.
I hope anyone at NV or MS sees this, I have tweeted them both now For me personally it’s not that devastating since I’m game developing currently and the Titan X’s are amazing fast at games. But soon I have to go back to offline rendering with Cycles and it would be nice to see them outperform my old 580s, what is it now… like 5-6 year old Fermi
Windows 7 is about 100% faster then windows 10… linux is about 20% faster then windows 7.
It more then likely a windows 10 problem (whether its nvidias drivers causing the problem or windows itself causing the problem, is still up for discussion).
Best bet is to treat windows 10 with caution atm.
the GTX580s are beasts… They didnt have as many cuda cores but they were much more powerful then the newer ones. With that being said we are looking at the 1080s as a potential to replace our 580 grid machines.
Only for blender 2.77 though. For Blender 2.73, Windows 10 is actually faster than Windows 7 when using a 980Ti as my testing above demonstrates - so it can’t be a straight “980Ti cards just don’t work well with Windows 10” issue.
Something changed in Blender around 2.76 that started to impact render times for 980Ti and Titan cards - and it got significantly worse with 2.77.
I think looking at what changed in Blender between 2.73 and 2.77 should be the priority as this accounts for a doubling of render times (or more depending on the tile size used) - compared to only a 20% difference when comparing Linux and Windows 7.
I don’t own either graphics card, but didn’t a lot of experimental features leave the experimental feature set to the supported set between 2.76 & 2.77? Total uneducated shot in the dark, but perhaps Windows 10 doesn’t like or interferes with the larger kernel?
It does seem graphics card specific though. My GTX480 renders scenes in 2.77 in around the same time as 2.76 and 2.73. It’s only the GTX 980Ti that seems to suffer from the leap to 2.77.
Related to the above - I also noted on the bug tracker website that when I monitored the render using GPU-Z, the memory controller load seemed low - topping out at around 15% when rendering with 2.77, whilst under 2.73 and 2.76 it was going up well above 30%.
When I monitored the render using GPU-Z using the optimal tile size above - it wen’t up above 30% at some points in the render.
A ran a trace on memory controller load using the best and worst tile sizes from my tile size testing. As you can see the faster render seems to load up the memory controller a lot more.
I’ve got 980ti on win 10 machine and got the same effect. Did someone got a response frome Nvidia yet? I’ve sent a message to their support, but still got no answer. The e-mail said they will answer in 24 hours, but it didn’t happen unfortunately
For me personally it’s not that devastating since I’m game developing currently and the Titan X’s are amazing fast at games. But soon I have to go back to offline rendering with Cycles and it would be nice to see them outperform my old 580s, what is it now… like 5-6 year old Fermi 
