It looks like Nvidia may have yet another issue with its flagship RTX 5090 card — a noted leaker claims it shipped out partially defective chips with slightly worse performance. Maybe check your card with GPU-Z and see if it’s showing the proper number of 176 ROPs?
It’s not every card, but reports are coming in of Zotac, MSI, Gigabyte, Manli, and even an Nvidia Founders Edition card with missing ROPs.