CPU for Fusion - Cores or Clock Speed more important?

I know Fusion is mostly GPU accelerated but I was wondering if anyone could offer advice on what was more important in terms of CPU selection, base frequency/clock speed or number of cores?

I'm thinking a balance between the two might be the best bet but everything I have ever been told in regards to VFX workstations has been pick a faster processor with less cores. This is coming from my background in Flame & Nuke though.

The workstation will be a dual boot Centos/Windows 10 and will also run Resolve (for online/finishing/mastering), Nuke X, Mocha Pro & Blender (only for occasional simple 3D so not too worried about specs for that). Mostly working with HD Alexa shot ProRes but beginning to do more UHD and occasionally get other formats such as Sony SLog mxf, Canon AVC Intra, etc;

I'm most likely going to go a Xeon or dual Xeon system but am also considering the new Ryzen 1950X threadripper as a potential option. So much bang for your buck. Waiting for workstation class motherboards for it first. Also Interested in thoughts about that as an option.

Main question though is speed or cores when it comes to CPU with Fusion?


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Its a difficult one for most of us to answer as its hard to tell what is going on under the hood. In my experiences (Windows 10, Xeon e5-2697 v4, 64GB, SSD's, 1080 GTX) I have found that Fusion does use all the cores though it doesn't seem to utilise them completely. I rarely get 100% overall CPU usage in Fusion and it tends to average out at about 50% usage during render. I cannot see any bottle necks in the system other than RAM occasionally on some comps.

I guess each Comp renders differently and some are better suited to using more cores than others.

As a general rule I would just look at the processing power overall e.g. Cores * Clock Speed and give a small bias to Clocks Speed over Core Count. Other may disagree with this but I wouldn't worry too much about the GPU for Fusion, in my tests OpenCL is pretty much slower than CPU for most work I do.

A bit of advice for speeding your workflow would be to have a Ryzen 1700 running as a render node, I have a couple of render PC's and found the ability to start rendering something over the network and go to work on another shot has improved my turn around a lot. These new AMD CPU's are great value for the money.

I am starting a new build with a Ryzen 1950x in the next day once its up and running I will let you know how it goes.

Hopefully someone can add more insight into what is happening in Fusion behind the scenes.