"SM_21" designates the Fermi GPU architecture (Compute Capability 2.1) for older NVIDIA GeForce 400/500 series cards, often requiring legacy CUDA 8.0 or older toolkits for compilation due to deprecated support in modern environments. A "SM_21.rar" file typically contains these legacy drivers or custom VBIOS for hardware that NVIDIA no longer officially supports. For discussions on troubleshooting these legacy architectures, visit NVIDIA Developer Forums . Cuda installation NVCC sucks too much?? Value 'sm_21'???