What is the NvENC performance of GTX 1080 comparing to M60?

I know that GTX 1080 can only do at most 2 streams at a time when using NvENC and M60 does not have this limitation. However, how if I just need to encode one stream at a time?

How is the encoding performance of GTX1080 comparing to M60 if both of them are just encoding one stream or one video at a time?

GTX 1080 = GP104 = “Pascal”, GPU Core clock ~ 1607 (by wikipedia or use GPU-Z)
Tesla M60 = GM204 = “Second Gen Maxwell”, GPU Core clock ~ 1178 (by wikipedia or use GPU-Z)

Download Video SDK package from https://developer.nvidia.com/nvidia-video-codec-sdk then open included “NVENC_Application_Note.pdf” then read pages 7-8 then compute performance metrics yourself.