AMD's iGPU is on the same power rail as the CPU cores, and the same throttling mechanisms apply to iGPU power consumption. Intel puts their iGPU on a separate p

AMD's iGPU is on the same power rail as the CPU cores, and the same throttling mechanisms apply to iGPU power consumption. Intel puts their iGPU on a separate power rail, but the chip's turbo power limits still apply. In both cases, the iGPU cannot draw as much power as the CPU cores so the limits have to be lowered quite a bit before they start affecting the GPU (unless you're running a workload that heavily uses both GPU and CPU).