Yes and no. Spiderman without
RT isn’t too CPU intensive but adding RT both increases the CPU load as well as the CPU bandwidth
load. As it happens, maxing out RT only adds a fairly moderate load on the CPU in Spiderman (~50%) but the added CPU bandwidth it needs is twofold.
CPU bandwidth is one of those things that tends to be forgotten about. Most of the time it doesn’t matter a whole lot but then we have cases like Spiderman where can it matter even more than the physical CPU itself.
Edit: Here’s an example
that shows it pretty plainly. Both of these scenarios are running at 60fps but one of them has a significantly higher load on the CPU and bandwidth subsystems. And I’ll stress that neither of them has anything to do with the GPU.