Arnold GPU supports a set number of Arnold features, including arbitrary shading networks, SSS, hair, atmospherics, instancing, and procedurals. See here for a detailed list of Arnold GPU features and known limitations.
Arnold GPU works on NVIDIA GPUs with the Maxwell architecture or later. Multiple GPUs will improve performance.
See the full list of supported GPUs.
See the Arnold system requirements for the recommended drivers.
You can easily switch between CPU and GPU with a single click. You'll find a new Render Device setting in the Render Settings > System section in the Arnold plugins.
You can use CUDA_VISIBLE_DEVICES (environment variable) to limit which GPUs Arnold (and any other CUDA-based application) can see.
Matching noise can take a little experimentation because Arnold GPU uses Camera (AA) sampling only. We recommend you also use Adaptive sampling. Here are some guidelines: