CPU usage and multiple cores question


I have a 10 year old 2008 Mac Pro 8 core 2.8Ghz with a Geforce GTX 970 running Zwift at the moment. It does OK in Watopia and runs 4K settings and I get from 30fps up to about 80fps out in the country side, but in the centre of Insbruk with lots of people around and all the buildings etc it drops to around 16 or 17 at times, but picks up in other places to much better frame rates.

Am thinking of building a new pc to run Zwift and am wondering if I use something like a Ryzen 5 1600 or latest i3 4Ghz with the GTX 970 will it make much of a difference to frame rates? Am trying to keep the costs to a minimum.

I have been watching the cores used on the Mac Pro while Zwifting and it uses all 8 cores, but not to any great extent. I am aware that the graphics card does most of the work in Zwift, but wonder if I build a new system will it be much better than the old Mac Pro? Ram speed etc on the 10 year old computer and single core speed are very slow compared to modern systems, so how much difference will it make?

Is there any benefits from a 6 core Ryzen which has better multicore bennchmarks compared to a 4 core i3 with faster single core speed but slower multicore?

A search for the 970 on https://zwiftalizer.com/benchmarks shows a report of a system with 

  • PC / Intel Core i3-6100 @ 3.70GHz / Nvidia GeForce GTX 970/PCIe/SSE2
  • 6th generation (Skylake) Intel Core family processor

getting an average of 66 frames per second with a minimum of 45 at the “2160 Ultra” graphics level. So the i3 looks good. You can also search for Ryzen systems at zwiftalizer and compare actual user data.

Thanks Steve

I have spent ages looking at all those benchmarks and the same systems at times can show big differences in frame rates. I think you can gain some idea from them but I don’t like to put too much faith in them. If I had posted my files from rides using the Mac Pro in Watopia then it would seem to indicate I was getting an average of say 45fps, max 70fps and min of about 30fps, but in reality it can go down to about 16fps at times in Innsbruk.


FWIW, using an older i3 and a 960 today on a 190+ group ride on Innsbruckring, I saw a minimum of 44FPS and average of 59FPS on 1080ultra. 

I have seen choppy frame rates in the heavy dust on Watopia, but IIRC that was using Apple TV on big group rides.

Thanks Steve

I think I will go ahead with the build using an overclocked i3 8350K. Been looking at gaming site Q&As and I think the faster processor will at least help prevent big drops in frame rates. If all else fails I will just have to get a better video card to run 4K consistently well

Peter: I run a older I7 with GTX960 and my min is around 45fps 1080ultra even while streaming.


I am pretty happy, but if I can find a 970 at a good price i would upgrade. 

Hi Gerrie

If I try running any of the lower resolutions than 4k on the old Mac Pro the frame rates don’t improve much but the graphics deteriorate markedly, so I don’t think in 1080 I am getting the Ultra setting. I might try editing the file profiles and see if that makes a difference. 

Anyway, I have ordered some parts to build a new pc. Will be interesting to see what the overclocked i3 and the gtx 970 can do. 

Can hand the Mac Pro on to another zwifter in the house, so worth fiddling with the file settings. I wasn’t really aware of the ultra setting in 1080, although I saw it on Zwiftalizer, only just now understanding what it is. Also have a Macbook Pro 2013 which does 1080 ok but averages about 20fps so I haven’t seen the ultra setting on it.

I don’t know how Mac handle graphics , I only use Windows pc’s. :slight_smile:


I think you will be very happy once you get that pc running.