So, I thought I had done nice optimised builds, but it turned out that SIMD optimisation was missing. I’ve now committed some SCons support for this though. The optimisations can now be turned on by building with scons using WITH_BF_RAYOPTIMIZATION=True.
I have re-uploaded 32bit and 64bit builds to graphicall.org that now have SSE optimisation for the renderer enabled. You should now be able to successfully use SIMD QBVH and SIMD SVBVH, which would print that SSE was disabled during compile time when using the previous builds I posted.
To use any of the optimisations, check the Performance panel in render settings. The Auto setting tries to select the best optimisation strategy, but you can choose any of the other ones too. Octree is what we know from the previous Blender series, all the new names are from the GSoC work done by André Susano Pinto (jaguarandi).