is the rendering all done on the gpu ?

is all rendering done on the gpu or is it more like premiere where the most time consuming functions are still executed by the cpu ? i am trying to understand if for a given amount of money to build a desktop PC for daz rendering it is better to have a weak cpu/strong gpu(ryzen3+1080ti), medium cpu/medium gpu (ryzen5+1070) or or strong cpu/weak gpu(8700k oc + 1060). thanks
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In Iray the rendering is doen on the GPU (as long as the scene fits), though prep work is don't by the CPU. Of coruse of the scene doesn't fit the CPU will do the whole job, as it will for 3Delight. The GPU can also be used, and is the default, for dForce draping.