Hey all! I recently purchased a used 12-core system (2x Intel Xeon E5645, http://ark.intel.com/products/48768/Intel-Xeon-Processor-E5645-12M-Cache-2_40-GHz-5_86-GTs-Intel-QPI) and loaded it with Centos7 for help with rendering at work. I was hoping that the extra cores would prove it to be powerful enough, despite the fact that the chips are about 5 years old now.
Anyway, I noticed Blender’s thread auto-detect feature only sees 8 of the 12 cores. I did some searching and found that (at one point) Blender had been hard-coded to max out at 8 threads (www.blenderartists.org/forum/archive/index.php/t-152109.html). At the time the solution was posted, Blender had a BLENDER_MAX_THREADS variable that controlled the cap in the file /blender/source/blender/blenlib/BLI_THREADS.h.
#define BLENDER_MAX_THREADS 8
In another file, /blender/source/blender/blenlib/intern/threads.c/, was a similar line:
#define RE_MAX_THREADS 8
Long story short, it appears that code has been updated to:
#define BLENDER_MAX_THREADS 1024
#define RE_MAX_THREADS BLENDER_MAX_THREADS
Which would seem to fix the issue at a quick glance, but the problem still persists - I only see 8 of the 12 cores on my system. Are there other issues with my system that might be causing this to happen?
UPDATE: Running ‘lscpu’ on my machine shows Centos only sees 8 cores as well. I wonder if I need to enable Hyperthreading to get the full 12?
ANOTHER UPDATE: SOLVED! Turned out my BIOS settings were limiting my CPUs. I updated the BIOS and now Blender sees 24 threads!