Blender build: How important is the CPU if paired with a RTX card?

[spaboleo]

Hey everyone,

I was wondering how important the CPU really is to use with Blender if it is paired with a RTX card like a 2070?
Given that rendering mainly happens in Cycles with OptiX on the GPU.
I assume that the 3D viewport rendering is also mainly GPU powered, right?

Wouldn't a simple AMD Athlon X4 950 with 16GB DDR4 for example be enough to get away with as a minimal system?

It won't be my main work system and it'll only be used for Blender.

Thanks a lot in advance.

 

[Jerry James]

When you're actively working on a scene (panning, zooming, sculpting, etc.), the single-core performance of processors affects your viewport fluidity the most. Of course, it does depend on the complexity of your scenes too so you might be able to get away with a much weaker CPU without too much hassle. Do you already have that processor on hand?

 

[spaboleo]

Thanks for your reply. Luckily, I don't have the hardware yet, but I'm considering various options. I'm normally a Mac user, but want to utilize the performance of an NVIDIA RTX card for 3D work. It doesn't make much sense to pay huge sums for CPU power that I wouldn't need or use otherwise, since I neither game, nor do other CPU heavy tasks (compiling, data analysis etc.)

I'm currently using a small 8th Gen. Intel i3 processor. What would be a good test to see the CPUs limitations in the viewport?
Also, does the statement that Blender uses a single core mainly still hold up? Most of the reports I've seen are from 2 and more years back and Blender has evolved greatly in that time.

Thanks a lot and cheers

 

[Jerry James]

Well, a good way to test would be to open up complex scenes and try tweaking them, moving around them, etc. A better processor basically helps smooth that experience out. It won't get 'stuck' when you're moving around basically. Here are a few from least complex to more complex. You can open them and test them out (move objects around, modify a few, etc.) to see what sort of complexity you usually work with and how that feels on your system:

https://file.io/7FrZZTdileXR
https://file.io/jn9dKfQGizyE
https://file.io/Im2JUBVa16xN

 

[Jerry James]

Also, does the statement that Blender uses a single core mainly still hold up? Most of the reports I've seen are from 2 and more years back and Blender has evolved greatly in that time.

You can think of it this way - the CPU feeds data to the GPU for processing the viewport. You can't completely ignore one part of the system and overspend on another because it just creates a bottleneck. Sculpting, for example, is highly reliant on your CPU. The more subdivisions you make, the faster your CPU has to be to not stutter around the scene.

Blender has evolved by managing to use CPU and GPU concurrently, speeding up many processes. You still do need a decent level of CPU performance. But as I said, it's completely dependent on your scenes so you'll have to test it out