4k vs FullHD - CPU workload


I am using VCV with a massive template on a FullHD screen but would like to change it to a 34" QHD (3440x1440) and I wonder how that would impact my CPU’s workload?

Anybody did the same and can share some impressions especially on CPU load?

I ask because I realized that when I switch from 60Hz frame rate to 30Hz the CPU is -4% and GPU -9%; so I can imagine that a QHD resolution could have another impact on the CPU. Right or wrong?

My system:

i7 8700K @ 5GHz+ AIO water cooling (top notch single core benchmark, decent multicore bench.)

AMD RX580 8GB graphics (not really suited for 4K gaming)

The template I use runs pretty well with that config:60Hz frame rate @ FullHD and 48kHz, CPU = 35%, GPU = 40%, cores used 4 out of six. Would it run well on 3440x1440 too?

This template:

Thanks in advance, t.

would expect no higher CPU, but perhaps the GPU would have to do more work?

Im on a 4k screen. From my experience, reducing the frame rate insinde VCV rack has a huge impact on the GPU load (blinking leds at 30Hz or 15 Hz do look pretty much the same).

No one can answer a question like that accurately unless they have exactly the same hardware and the same patch. Only you can find out by trying it and measuring. Here’s how I understand things in general:

  • Graphically, the more pixels (the higher the screen resolution) and the higher the framerate (refresh rate) that Rack has to push out to your GPU (“graphics card”) and subsequently to the screen, the more the GPU has to work. As long as your GPU is up to the task everything should be just fine and things will be fluid and your CPU will not really be bothered.
  • From what I understand from what Andrew has said about the graphics sub-system of Rack: When/if the graphics requirements that Rack puts on your GPU, given the resolution and framerate you have chosen, and the patch you are playing, hits the wall of the performance capability of the GPU, the CPU has to take over/help with graphics rendering duties, and this is where your CPU performance in Rack will start to go down, the CPU will get hot and your fans start to spin up.
  • From the above follows, that for the specific GPU performance in a given computer, each person must find that “wall” for themselves, also given the size of the patch, where the GPU starts to give up, and then reduce the refresh rate/frame rate and/or the screen resolution. There are many tricks about that posted in this forum, such as reducing resolution only for Rack, reducing the window size when running, minimizing the window when running, etc. etc. outside of what you can simply select from the Rack menus. But it will always be specific to your hardware, your patches and your system, no one else can tell you exactly, other than the general advice of e.g. “avoid Macbooks with integrated Intel graphics”, etc. For myself, I would always start by simply reducing the framerate to e.g. 30 in the Rack menu, and if that’s not enough, reduce the resolution, and if that’s not enough then scale back the size of the patches, or bite the bullet and get better graphics hardware.
1 Like

Yes, as usual @LarsBjerregaard puts it very well. I agree 100%. I have a “feeling” (very un-scientific) that if you have a “decent” GPU the graphics is never an issue. What’s a “decent” GPU? oh… not the built-in intel GPU you find on a lot of laptops? My “feeling” is that if your GPU can kind of play current games you are fine. Or if you buy a new GPU, a “budget” gaming card if more than adequate.

But I don’t have much to back this up. Other than that most of the issues with GPUs here seems to be with laptops.

Oh, and I recently went from an ancient monitor to a cheap 4k. Rack is really great at “retina” resolutions like this. It would now be quite painful to go back.

1 Like

Squinky, Ahorn and Lars, thanks a lot for replying and sorry for my late response.

Good to hear from you guys how this things work. I realized too that when the GPU can’t take the graphics anymore the CPU has to work for it.

I switched to the RX580 card just 10 days ago because using the on-chip graphics of the CPU couldn’t handle this template at 4 cores anymore (had to switch to 5 cores which increased CPU workload to 55% and also the lowest refresh rate) and also the CPU cores went up to 80°C+…

The RX580 improved this drastically. CPU is at max 60°C now when VCV is doing its thing and workload at 60Hz refresh rate is around 35% at 4 cores.

Okey-dokey, I see that I have to try and find out myself, that’s a the key advice =) Thanks for chiming in!

cheers, t.

1 Like

Yup. And it’s not even because we’re hardasses, it’s because of the gajillion different bits of hardware out there, that you can assemble into a gamullion different combinations, using a gatrillion different good/bad drivers. Which means it’s pretty much impossible to say beforehand, with all those combinations.

1 Like

I’m always amazed windows works as well as it does. Or at all, for that matter. What with all the gajllions.