Starfield is arguably this year's most hyped game. At this point in time, the game runs well on AMD hardware thanks to its partnership with Bethesda, but Nvidia owners haven't gotten as much love. Though the game runs well enough, Nvidia GPUs are uncharacteristically underperforming in Starfield, and official support for Nvidia's bedrock technologies such as DLSS are missing.
Over time, the situation will improve as Nvidia’s and Bethesda’s driver updates are released. If you don't want to wait, there's an interim tweak you can do yourself, and if the early testing is to be believed, it can deliver major performance boosts for Nvidia owners playing Starfield.
Okhayko from Nexus Mods has published a guide (via Reddit), which gives Nvidia users a welcome boost in FPS. The secret to a better FPS is to enable Resizable Base Address Register (BAR). PCI Express uses a technology called Resizable BAR (Base Address Register). AMD calls it Smart Access Memory. It allows the CPU to access all of a GPU's memory, allowing assets to be transferred faster. Some games don't benefit at all from Resizable BAR, while others do, and Starfield appears to be one of them.
It’s not difficult to make ResizableBAR work in Starfield. I wouldn't call it easy…