What to choose GPU or CPU , and should I use opencl, Linux (openSUSE)?

Question

AMD ryzen 5 2600 6 cores RX570 vid card. 16 gig ram.

I have done allot of research, but can't find what ideally would be the best setting for my system.

At the moment Blender says my vid card does not support opencl, but I know why thanks to help on the openSUSE forums, and how to fix it. ( for others on Linux you need the proprietary amd drivers or at least the opencl part of it, not mesa opencl, that won't work with Blender. RX570 and RX580 do support opencl on Linux )

Now my questions, will opencl reduce the render times, and should I use the cpu or gpu setting in preferences? Or both if I understand the opencl part right ?

I am totally lost on if I want opencl at all and what setting to use. The one thing I do know, Blender works fine without it.

For a vid I want to make I probably want to use eevee rendering.

Answer 1

Long story short. There were plans for Vulkan, but Blender Org ended up going with HIP instead for Blender 3.0 & up. For below that you must use 'OPENCL' as render device in settings. (June 2023 update)

• Yes using OpenCL will reduce your render times significantly compared to when you have set it to 'None'.

• But since 570x is not that fast compared to 2600X CPU, it comes down to very specific situations where you will have advantage in using GPU over CPU (while in other cases it would be opposite). It won't be as vast as in my case, as I have a pretty old CPU.

• Using a rough estimate, you would get better results using CPU in cycles (an additional setting, not present in eevee), but make sure to set the tile size accordingly in Performance Submenu In Render Settings (right side on blender, not in preferences menu). A tile size of 128 or 256 or 512 is ideal for GPU (render something on each setting to test), and 16 or 32 is ideal for CPU.

• Somethings only use CPU, like the cloth simulations.

• Also Blender allows you to use CPU & GPU together where possible. Just click the box in front of both CPU and GPU, like in my following screenshot.

• Also, most of the blender devs use Linux, various flavors, so Linux is strongly supported. You can even get bleeding edge Alphas from builder.blender.org

• Note that Blender would not raise or cause any errors based on what you are using CPU or GPU. You have to test it by doing different renders or better yet running the benchmark (BMW scene only .. or the comprehensive 5-7 scenes)

• In my experience, for a beginner, you are better off just using the settings I showed below, and use eevee without worries.

• Having installed ROCM recently myself on a seperate system (Ubuntu used for some unrelated testing).. I don't think you need AMD ROCM.But rather the drivers downloaded from AMD website (they released Linux drivers, that include OpenCL support), or alternatively try installing the xf86-video-amdgpu if you are using XORG

Edit 2023: Just wanted to add more to this.

• Blender dropped support for OpenCL back in version 3.0 (December 3 2021)
• People on older AMD GPU cannot use the GPU mode in Cycles without significant inefficiency (you have to set Cycles Render Device to 'None')
• However, if you have a decent CPU, just use that with CPU option in Cycles
• For newer AMD cards, they can now use HIP as the Render Device, which offers significant performance gain over the older OpenCL. However, the fastest method is Optix for Nvidia card (hands down).