I have recently built my new PC (Ryzen 3700x + VEGA 64) and tried rendering BMW demo. The difference rendering speed caught my attention.

When rendering with CPU only, the time consumption never exceeds 3 minutes. When rendering with ONLY GPU (unchecking the Ryzen 3700x in preferences while keeping the VEGA on) the time is around 2 minutes.

The GPU-only configuration

However, when checking both the CPU and the GPU, the rendering time increased to more than 6 minutes.

CPU + GPU configuration

According to the information gathered online, the "CPU + GPU" configuration should be faster than either CPU or GPU alone, but instead it turns out much slower. Have I done anything wrong and what should I do about it?

P.S. By inspecting the task manager the GPU does not seem to be loaded when rendering, the fan is not roaring either (it does when running games). Have no idea what this means either. Please help.

GPU does not seem to be loaded

  • $\begingroup$ For hybrid rendering you should use small tiles, like 16x16, 32x32. And still might be slower than GPU only $\endgroup$ – Serge L Aug 28 '19 at 6:55
  • $\begingroup$ @SergeL So what is the point going hybrid? $\endgroup$ – user288208 Aug 28 '19 at 7:23
  • $\begingroup$ Technology has a potential, but tile assigning between hardware has to be optimised a lot. From my experience works better with less powerfull PC's $\endgroup$ – Serge L Aug 28 '19 at 7:44

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