When rendering with Cycles using GPU with only GPUs (no CPU) on Windows 10 or Linux (Ubunutu) I get 100% CPU utilization with four GPUs on an Intel H110 board with an i5 6502P quad core CPU.
Specifically it’s 37% with 1 GPU, 65% with 2, 90% with 3, and 100% at four and above.
Strangely, on a dual Xeon Platinum system it’s about 12% at max with four GPUs and doesn’t go up much from there even with 7 GPUs. Obviously the dual Xeon is a lot faster than the quad core, but in benchmarks the two Xeons are only about 4 times as fast as the single i5. On the i5, it’s using more than twice the CPU power of the Xeons.
Is this an issue with Cycles or potentially something with consumer chipsets/processors?