I’ve been looking at render speeds and comparing my 980ti to Threadripper 1950x.
I have been using Iray for about two years, and was used to the CPU being about a third slower; this, however, is not the case with Cycles. they are comparable - with the 980ti just about edging it; with 2.83 (beta), the CPU is slightly quicker, certainly with Adaptive Sampling turned on.
2.83
980ti
512 x 512 2:31.21, 2:31.13, 2:27.25, 2:27.98
Threadripper 1950x
32 x 32 2:07.48, 2:07.45, 2:08.10, 2:04.80
64 x 64 2:06.42, 2:05.64, 2:07.81, 2:09.05
Those were with my own test scene, but the same held true for Mike Pan’s BMW test.
It’s made my decission about upgrading my graphics card for faster rendering speeds, more of a challenge; a GPU, there is always the chance a given scene either wont fit on the card, or takes additional work to get it to do so.