tomshardware[.]com/pc-components/gpus/nvidia-gpu-owners-may-be-losing-performance-because-of-a-simple-setting-thats-disabled-by-default-enabling-resizable-bar-with-profile-inspector-can-enhance-gpu-performance-by-up-to-10-percent-in-3dmark
From the article it *seems* to be an issue primarily with Intel CPUs, but it wouldn't hurt to try it with AMD CPUs either.
... ReBAR changes the amount of data that can be transferred in one "trip" from the GPU to the CPU, which is usually constrained to a 256MB "aperture". ReBAR removes this limitation altogether.Despite its benefits, Resizable Bar also has its quirks. It does not benefit every game, and some games don't benefit at all from turning ReBAR on. Worse still, some games drop performance with ReBAR enabled. This has forced GPU manufacturers such as Nvidia to test ReBAR on a game-by-game basis and only enable it by default in their GPU drivers if a game responds well to the feature.
Still, enthusiasts have found over the past several years that Nvidia has not whitelisted all games or applications that benefit from ReBAR enablement. Manually testing ReBAR enablement in games that Nvidia has not yet whitelisted can yield significant performance improvements. This is usually done with Nvidia Profile Inspector, which is an application that provides complete control over Nvidia's drivers, bringing to light features not visible in the Nvidia Control Panel. ReBAR can be forced on globally (in the driver) or on a per-application/game basis with Profile Inspector.