Why is Cycles so slow in Windows 7?

I’ve been doing some rendering on a couple of different platforms, Win 7 and MacOSX. I’ve done several renders using mental ray, and I’ve found that in general, the Win 7 box I use is about 20-30% slower than my mac. However, when rendering with Cycles, it’s literally 3x slower!

I’ve been scratching my head on this for a while, and then I read that Cycles doesn’t like Windows very much.

What’s going on here? This is real problem, is anything in the works to fix it? Am I just doing something wrong?

Thanks!

Have no problems on my windows machine with any type of rendering on any app, and compared to Linux builds it’s about as fast if not equal. What is your hardware profile between both machines?

Win 7 x64 no problems here, your bottlenecking somewhere. Thats for sure. Are you rendering with CPU or GPU? Till I realized that I had to switch on the GPU, Cycles was under whelming, I think we can safely say its not the O.S.

Its good to know its not the os. My machine is a lenovo thinkpad with a i7 2600 series quad core processor. Ive been rendering on the cpu. Gpu runs great as well, but these tests were cpu only. It has me baffled. It should be running faster than this.

I just did a blender internal render between my mac and my laptop, and my render times we only about 10% slower on the laptop. However, if i fire off a cycles render, its 2-3x slower. So strange…

it all about the compiler, on linux using gcc, and on windows using msvs, i think once the devs get the gcc for windows working good try to test, and maybe switch to it, at least i think!

Cycles absolutely is slower in Windows that’s obvious if you check the benchmarks thread, but we’re generally talking 15-30%, not more… Perhaps it’s about how the system manages the threading? I heard the official builds don’t support multithreading, perhaps it’s this that’s in play here? Try some of the more popular builds off GraphicAll…

The second thing I can think of is that you run Win7 32Bit - like the preinstalled versions are generally 32 Bit as they generate less issues for the manufacturers (drivers & such).

it all about the compiler, on linux using gcc, and on windows using msvs, i think once the devs get the gcc for windows working good try to test, and maybe switch to it, at least i think!

This is true, windoze catches up with a different compiler http://lists.blender.org/pipermail/bf-committers/2012-March/035726.html

I tried an optimized build from graphicall and there was no difference in render speed. Im running win7 professional 64-bit so hopefully there isnt something in that install thats causing a problem.

Im pretty sure that cycles is multithreaded in windows, because my task manager spikes to 100% during a render.

Can anyone direct me towards a gcc-compiled build to test with?

Thanks!

Bump. Are there any Win64 graphicall builds that have been gcc_compiled? These render times I’m getting are killing me.