Shader Model support by DX version: https://www.lifewire.com/determine-d...r-model-812997
Pixel Shader support by graphics card family: http://ccm.net/faq/4226-identify-the...-graphics-card

NVidia was discussing Pixel Shader 5.0 support back in 2007 (http://vrzone.com/articles/nvidia-ge...-gpu/4768.html)

NVidia 770 was introduced in 2013 and supports DX12.