Questions and Answers
Q. Will it work with Asrock B450 steel legend?
A.
ASRock B450 Steel Legend supports up to PCIe Gen3 x4. However the Samsung 990 Pro SSD is a Gen4 x4 SSD. Thus, the SSD will not be able to attain it's maximum performance on this motherboard.
As a solution to get the maximum performance and value, you can either use a Gen3 SSD with your current motherboard. Or, you can upgrade your motherboard to one with PCIe Gen4 SSD support and use this SSD with it.