In general, Arnold is going to work on pretty much any 64-bit system where Houdini, Maya, Cinema 4D, or Softimage works. However, there are some minimum OS requirements:
- OSX 8 or later (as of Arnold 184.108.40.206)
- Windows 7 or later (as of Arnold 4.2.3)
- Linux with at least glibc 2.12 and libstdc++ 3.4.13 (gcc 4.4.7) (as of Arnold 4.2.6)
Other than that, Arnold works on Intel and AMD processors, and has no graphic card or GPU requirements, since Arnold is a CPU-based renderer.