CPU Selection can a i3 handle group rides

I been experiencing CPU bottle neck on group rides when disconnected form the internet I get 70-100 FPS in a sparsely populated area of the map I get 30-50FPS and a group ride I get 10-20FPS on 1440 high.

I’ve been looking in to various around the £200-300 bracket and from some staggering results from the smaller i3 CPU’s can anyone back up the performance of the little I3 processors in group rides.

Below are some screen shots from Zwift analyser i chose the GTX1060 and there is loads of logs and it should not be GPU bound at 1080 ultra.



The i3-8100 worked great for me. It would sit around 70% usage on all 4 cores in a group ride scenario.

That said, if I were upgrading my CPU now I’d probably go with the i5-9400F. Super cheap for 6 cores that can boost to 4.1Ghz.

With RTX Nvidia cards out in abundance now and crypto mining dead, there’s also a lot of great deals on GTX 1070’s and the like. So my 2 cents is new CPU’s are great and so are one Gen old Nvidia GPU’s.

Adding, my old 1060 3GB was also a little high on usage at 1080 Ultra Res in group rides, around 85%. This is why I’d go for a 1070 or above.

I have a i5-3470 and the CPU isn’t the bottleneck, it’s my old AMD HD7850.
You should have a Quadcore. i3 in the 8000s is Quad, below (2000-7000) is dualcore.

With a several year old i3, I’ve consistently seen sub-50% usage running Zwift 1080p Ultra plus streaming hi-def video on a second 1080p screen. The GTX 960 is the bottleneck on big group rides, particularly in the dust, or in the starting pen, where frame rate drops for some reason. Otherwise 60 FPS is easy.

I’ve played with using RivaTuner to cap FPS at 30 since it looks fine, the GPU usage remains low in most situations, I don’t care about the visual difference, and it doesn’t affect “game play.”

edit: to specify, my experience is that an Intel Core i3-6100 CPU @ 3.70GHz is plenty of CPU to run Zwift at Ultra 1080p plus a second 1080p stream at the same time.

Thanks for the reply I have a i5-4690k in the house I tried my rx570 in and it was poor. I even tried a clean install of windows 10 and got 10 fps in the pen and averaged 20fps. It picked up to 30 -50fps as the group split up.
Slightly better than my phenom cpu

Thanks for the reply I’d be more than happy with a minimum of 30fps and a average of 50fps. The more I dig the more I wish I’d bought a nvidia gpu

Yes. Also look at Pentium G4560 and G3258 dual cores performing well with 9xx and 10xx Nvidia CPUs. A Geekbench 4 single core score of 4000 is a good baseline for whether or not the CPU will bottleneck a modern GPU. For example, https://browser.geekbench.com/v4/cpu/search?q=G4560

With your rx570 and phenom II, shadows might be killing performance because of those lame AMD OpenGL drivers (I read there’s literally nobody there anymore who knows how any of that code works, so no one dares touch it). Have you tried editing your configs\high.txt to turn down shadow resolution and turn on simple reflections?

set gSimpleReflections=1
sres 512x512

or even
sres 256x256

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i’ve tried 720 with medium detail up to 1440 with the ultra config copied into the high with sres 2048x2048 on a group ride the no noticeable difference in fps maybe it goes from 12 to 15 FPS. if I disconnect from the internet it runs between 60+120 fps reconnect and it drops back to 10-20FPS.

I see what you mean now. I have an older Xeon 5672 CPU (4 core, 8 threads) with an AMD Radeon 7870 1GB and if I disconnect from the internet the FPS goes from 40 up to to 60. I reconnect and it drops back down to 40 as soon as the rider list reappears. Every time. When the rider list came back, there was never more than 4 or 5 other riders nearby to render, so it is definitely not the overhead of having to draw the other riders. I was just stationary at the side of the road. There does not appear to be any difference in CPU load with or without networking, so I have no idea why it blocks the rendering, but obviously it does. Maybe it’s the overhead of trying to figure out everybody else’s position in time for the next render. When I put an Nvidia GTX 960 2GB in the exact same machine, it holds a solid 60 fps. I can’t explain it. My guess is maybe Nvidia’s physx helps out with the positional calculations ¯_(ツ)_/¯

Also, zwiftalizer looks like it needs an update to better report those deliberate networking disconnects. They appear as network delays, when they should really be errors.

Really interesseting thread here I digging out.
I have a i5-3570 (4C/4T), 8GB ram, and a GTX970 (4GB GDDR) and what ever is the resolution from 1440p to 720p, the framerate is dropping under 30 on large groups.
There is a limitation in the rendering which is not linked to GPU power.

Next week I will borrow a GTX1080 from a colleague and see.
It could be due to graphics memory. msi Afterburner shows a 3.6GB of graphic memory used in Watopia.

Last tuesday, during the PRO-am innsbruck race, even the offcial zwift stream was suffering of low framerate while displaying the pack.
The framerate was back OK when showing the sprint leaders from a rear view. The change of framerate was obvious.
I ve no clue what kind on computer they is using Nathan, but I assume it’s not 5 years old like mine.

More to come, i’d love to solve this issue.

PS : be carefull with Zwiftalyser database results.
I assume a lot you people just upload their lonely rides.
Because on similar machines, some gets a solid 60fps at minimum while some others also experience frame rate drop.

Hi Stephane,

Yes the i5 should be plenty. I use to run a a GTX960 and also had some lower FPS in big groups, I upgraded to a GeForce GTX 1060 6GB and thins is a lot better.

I can see if I can find a log file of a TdZ ride.

Nathan is a gamer so I would expect he has a sweet new PC or two or three.

EDIT: I found a log file
This is from Tour de Zwift: Stage 1 Short Distance. 800 riders.

Indeed, which is why I stopped collecting data and removed the benchmarks in May 2019. People asked me to put it back, so I did, with a notice saying it’s historic data an may not accurately reflect the current state of the game engine. Or something like that. I will add - and may not accurately reflect ride situation - groups, world, route choice, etc.

Sidenote: I watched Nathan’s live stream of him building his PC for streaming. It was less than a year ago and top end 8th or 9th gen i7 with a GTX 1080 if I remember correctly.

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I run a 10 year old AMD CPU with a GTX1060 and experience the same. I can be as low as 10-20fps in a blob of 200 especially if I in a Australian ride e.g. bacon rolls I’m in the UK and have put it down to CPU and internet ping throttling.
In European rides of a similar size I get 25-40FPS. CPU throttling without the internet
Rides like tour de zwift with 600+ I get anything from 30-60FPS . It seems to be how many rider are on screen that affects the FPS with a slow/ older CPU.

Going from 720 to 4K is no difference in a group ride. Only when I’m in a unpopulated area like going up alpe du zwift do I see a difference this then loads the graphics card. I get 120FPS 720p and around 55fps in 4K.

I spoke to zwift support about this 12 months ago but its still the same. population slider in setting would be a great help.

A 10 year old AMD CPU should be replaced.
They were totally bad. I think this is your bottleneck.

Thanks for the reply. But I did state that was my bottleneck.

Since update 1.0.44575 on Jan 15th 2020 I see a better balance of cpu / gpu load on my old Xeon E3-1225 v3 CPU (4C/4T) with GTX 970 (4GB) much like your set-up. In group rides, one of the CPU cores is now at much higher utilization - 85% to 100% (average across all cores 30%) and the GPU utilization is around 60% - 70% at 1080. My average FPS is above 60 again. The group was a bit stretched out. On a second ride with a tighter group the FPS dipped into the 50s, which is fine, and a lot better than before the update when it was in the 30s. Life in the old dog yet. (I’m actually considering ditching the PC by the end of 2020 and getting an iPad Air. I’m blown away by how well Zwift performs on the iPhone 11 A13, but the screen is too small to use every day. I’m done with all the pc cables and crap).


Thank you for your feedback Mike.
Good it’s improving.
On my side, I didn’t notice it.

Yesterday I borrowed a GTX1060 from a friend and gave it a try.
This GC has 6GB onboard, instead of 4GB for my GTX970.
Result is the same. So, my 4GB of Graphic DDR is not the bottleneck. (Test at 720p resolution also proved it)

Next test : I will try to double my RAM by adding another 8GB bank.
It will activate the dual channel and I should see an improvement, and not only in zwift.

On a side note are your PCI slot able to handle the GTX1060.

PCIe standards currently come in three different generations: PCIe 1.0, PCIe 2.0, PCIe 3.0 and PCIe 4.0. Bandwidth doubles with each generation.

So if your MB has PCIe 2.0 that may be your bottle neck.

My motherboard is an ASUS P8H77-I . It is PCIe 3.0, 16x on this slot.
My CPU is Ivy Bridge (3e génération), so this speed is active.

When I’m alone and Vsync OFF I’m between 80 to over 100fps sometimes.
I really don’t think the limit is there but thanks for the input. :slight_smile:

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Disregard my last post. I think there was something different about that previous group ride. Today in the Ascenders group ride of 100+ my FPS was back to … whack. The bunch was tight, with a designated leader, and the fence was on, for what it’s worth. Interestingly it was the same world and course. My CPU main core was around 60%, the other 3 doing very little. GPU not getting taxed much at all at 55%. CPU bottleneck for sure, but why?

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