Older NVIDIA drivers have lower thresholds for thread allocation.
Older GPU generations (like the Pascal or Maxwell series) hit these limits much faster than newer RTX cards with dedicated RT cores. How to Fix the Warning 1. Enable Adaptive Sampling
Understanding the "Warning: num samples per thread reduced to 32768" Error Older NVIDIA drivers have lower thresholds for thread
When a scene is extremely "heavy," the GPU takes longer to calculate each sample. The engine sees this delay and preemptively reduces the sample-per-thread count to avoid a system hang.
Warning: num samples per thread reduced to 32768 rendering might be slower To prevent a crash, the rendering engine automatically
However, Windows and Linux drivers, as well as the NVIDIA CUDA architecture, have limits on how much work a single kernel execution can handle before it risks a event—where the OS thinks the GPU has frozen and restarts the driver. To prevent a crash, the rendering engine automatically caps the samples per thread to 32,768 . Why Rendering Might Be Slower
If you are using an older version of a renderer that still uses "Tiling," try reducing your tile size (e.g., from 512x512 to 256x256). Smaller tiles require fewer samples per thread to be active at any given millisecond, which can bypass the warning. 3. Update to Studio Drivers To prevent a crash
The second half of the warning is the most frustrating: "rendering might be slower."
If you are using NVIDIA, switch from to NVIDIA Studio Drivers . Studio drivers are optimized for long-running kernels (rendering) and are less likely to trigger aggressive TDR limits that lead to sample reduction. 4. Check Your "Max Samples" Setting
The num samples per thread reduced to 32768 warning is your GPU's way of saying, "I'm trying to do too much at once, so I'm slowing down to stay safe." By optimizing your and ensuring your drivers are up to date, you can usually clear this warning and regain your rendering speed.