Plain physics - Improvements also mean extra work (calculations) thus added time.
Same here…
The renders are slower in 2.78.
But much the render mode is much, much faster. I got a Titan X and the difference in viewport in render mode is huge (more than 50%)
Too sad the renders are not faster…
Alex
Me too.
On average, 2.78 is 10% slower (GTX 750 TI).
In some scenes, even 25%.
All of you. Make sure you are using latest builds from buildbot:
https://builder.blender.org/download/
These improvements will be also in Blender 2.78a when it is released next week.
In Linux I’m getting speed improvements with my GTX 960.
@albron. 50% is too much. What operating system?. Have you tried latest nvidia drivers?. Have you tried on Linux or Windows 7? Have you tried with recent builds from buildbot?
This sucks. Gone from 53 seconds last year to 82 seconds today on my amd 390x. Using latest build.
Edit: Just as slow in 2.77a. It’s probably the drivers.
Isn’t that because now Cycles renders more things than it did last year though? AFAIK it still doesn’t support all features that it does on CUDA?
Theese days I have tested 2.78 with some of my scenes (not just BMW) and even with latest builds and latest nVidia drivers 2.78 is near 8% slower in all scenes.
And I do not see it faster in the viewport performance. :\
Hi, as mentioned several times in this thread, use build from https://builder.blender.org/download/
or wait for Blender 2.78a coming later this/next week.
Cheers, mib
Have you mentioned somewhere which version of Windows you are using?. If you use Windows 10, I had read that people recommended to install nvidia original drivers, not those that Windows install (or something like that, I really don’t know how that works in Windows 10).
Could you try Blender from buildbot with default settings?
Close Blender if you have any open instance. MAKE SURE to make a Backup of your Blender 2.78 USER config by renaming ‘2.78’ folder for something like ‘2.78.bkp’:
https://www.blender.org/manual/getting_started/installing/configuration/directories.html
Open Blender from buildbot. Enable CUDA from User Preferences > System. This will create (or maybe not) a new ‘2.78’ folder in your Blender User folder. Open the scene and render.
Then to recover your Blender settings, delete the new ‘2.78’ folder and rename the ‘2.78.bkp’ folder to ‘2.78’.
Extremely cool! Is there any aggregated form with this patches connected? The best masterful criticism you’d get is from material craftsmen, and they ordinarily don’t know how to incorporate a “welcome world”. Standard clients as a rule can’t gather their own particular forms to test unless they are both craftsmen and coders, obviously. I’d attempt numerous intriguing patches if there were accumulations with them connected.
Yazu, there was a bug with tthe titan X and the render are slower than what could be expected with a Titan X…
The rendered mode was for instance very slow…
Now, it seems to be much faster with the 2.78.
I did this to see the difference.
I tried with the last build. It’s a bit faster but still slower than the 2.77…
So for now, there’s positive and negative point to migrate to the 2.78. I’ll work on it, but will do my render in the 2.77. 
And as Mib2berlin said, I’ll wait for the 2.78a.
Alex
Hi Dito, this patch is already in master so buildbot got it.
Cheers, mib
Thanks for the info.
After testing and testing daily builds … 2.77a continues rendering faster than 2.78a. 