Intense Graphics glitching on Apple M2 Max [1.56.0]


I am experiencing quite an intense graphics glitching on the Apple MacBook Pro (M2 Max). When you look at the video it will make more sense, but basically sometimes just HUD starts flickering, but most of the time the screen freezes completely for random period of time and starts flickering and then the display returns back to normal again. What is strange is that the problem is purely graphical, the engine still detects all the data from sensors and updates the rider position in the world as if it continued along in the background as normal. During that time most of the HUD data disappears or flickers and then it gradually rebuilds (mainly the riders list makes it obvious).

Two problems with this - the freezes are sometimes as long as a minute, which obviously takes any group rides or racing out of the question. Also, it really takes the joy out of riding.

Now I appreciate Apple Silicon version is still in the early stages and my setup is also little non-standard, so rather than trying to blame anyone, please consider this as more of a heads up for development team @Jon @shooj that there might be some gremlins in the graphics engine. It is also a genuine question about what might be the actual cause and what can I do to improve this. I’d be very interested in your insight and I am also more than happy to do more testing. I can be obviously doing something wrong.

My computer:
Apple MacBook Pro 16" 2023 (Apple Silicon M2 Max 12-core CPU / 38-core GPU, 96GB memory)

Zwift version:
Launcher Version 1.1.11 / Game Version 1.56.0 (124332), but it is happening since April 2023 on all previous versions, both Rosetta Intel and new Apple Silicon native versions

4K Samsung TV (144Hz capable) connected via HDMI direct to the MacBook (there are also 2 other 4K monitors connected via Thunderbolt 4 dock, displaying just MacOS desktop at the time)

Modifications to default:
This is my modified “high” profile config file (which is currently being used as highest by Zwift for this computer type), to achieve the best quality:

res 1920x1080(0x)
sres 2048x2048
aniso 4
set gSSAO=1
set gFXAA=1
set gSimpleReflections=0
set gSunRays=1
set gHeadlight=1
set gFoliagePercent=4
set gLODBias=0
set gShowFPS=1


  • The computer is fully capable to run this setup at min 70fps in the most intense scenery and rider density, average of 120 or even 144fps is quite normal. During that time, the CPU runs at fairly minor utilisation, the GPU is utilised at about 80% (which I believe is a conscious Zwift’s decision to limit the performance impact). What I’m trying to say is that I don’t think the hardware is a bottleneck or performance an issue or a cause.
  • These glitches happen most frequently in the “new” worlds, like Urukazi on Makuri Islands especially. It happens very rarely in Watopia for example. It is very world dependent and can be very well replicated in certain areas.
  • I appreciate the Foliage option is quite high, but there was no perceptible performance hit using those. I have started at 5, 4 is the first experiment to see if it improves the problem (it doesn’t)
  • I couldn’t see any obvious issues in the recent log files when running them through Zwifatlizer. Here’s the latest log, the actual ride is only the first hour, the rest is idling in the menu
  • I am on 1Gbit symmetrical optical line and the computer is on stable 5GHz ac WiFi, both constantly monitored without any connectivity problems. Standard latency is around 7ms.
  • There’s nothing else running at the system at the time, just Zwift.

Sorry if I missed it, but you’re not running off battery power are you? You need to be connected to mains power for the best performance.

Modifying the config file isn’t a good idea unless you’re sure the device can handle it. Since you’re having problems you should put that all back to defaults and see if the problem goes away.

Interesting. My family invested in a Apple Mac Mini M2 over Christmas (because they could not cope with my mood when my PC kept crashing mid ride (ever since update 1.48) and I’d discovered that the Graphics Card, overnight, had become unable to cope with the demand Zwift put on it) and since I’ve not, yet, encountered any issues (I’ve also been able confidently run Video Screenshots.) However, I have had one screen freeze (I ride Zwift at least 4 times a week and rides are unusually over an hour, often more) which is similar to that you describe. It might be worth running Zwiftalizer (see Zwift Insider for details, it’s free) to nail down how this issue arises (it helped me (and hence my family) identify what was the best upgrade option (i.e., to Mac Mini M2 from a standard MS Surface running i7 and its integrated CPU/GPU chip.)

Nope, all connected to mains power and optimised for maximum performance rather than efficiency.

I know, I have only done the editing after thorough testing it would be able to handle it. And it is, with plenty of performance to spare. It just happens in certain places. I am not expecting Zwift support to sort out the problem caused by modified settings, but I think the problem is a bit deeper, engine related, so I’m hoping it would be picked up and investigated.

As I’ve mentioned, the machine is fully capable to support these options at 70fps minimum (120 or 144fps is quite normal average) so I don’t think the performance is a bottleneck here. I have been combing through the log files and observing / recording when this happens and it’s never preceded by any noticeable drop in frame rate or anything outside of Zwift happening on that machine. It just happens out of the blue without any apparent reason.

Thanks Andrew. I’ve already run the logs through Zwiftalizer (see my original post for a link to one of the results) and even checked them through manually if I spot something suspicious. It doesn’t look like anything would point out to the cause. It’s a bit baffling really - everything runs at full speed and smooth with quite a nice reserve, the computer ticks along nicely without being overloaded and yet it still happens out of the blue. I’m running other very GPU intensive apps on this Mac and never noticed anything similar.

Kudos (RideOns) for your riding btw - those days I could do the same are long gone, wish I could ride more often.

Revert to the standard profile settings and see if it goes away. I have seen similar issues caused by profile tweaking.

David, thanks. That intensity comes with the benefit of now being retired, so chapeau to you fitting in anything while, no doubt, having to juggle many more things in your life. I believe that IOS runs better on Zwift than Windows and hence any Apple product, other than Apple TV, let alone one equipped with an M2 chip, will be best. It is baffling, and seems so for Zwift too as I know they’ve been looking at these issues ever since they first arose when the 1.48 upgrade occurred. Best of luck, but you are, in my humble opinion, on the best platform.

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I’m gradually going back to standard while testing and see where it remains stable. It’s sad to see the better graphics go, because it really looks amazing, especially with the dense foliage. I’ll see where I’ll end up, but I sure hope it’s not just the standard high profile. The machine is clearly capable of much more than that.

But it would still be nice if someone from Zwift development team would comment on potential reasons for this or even try to find the responsible gremlins and weed them out.

Thanks Andrew.

I do agree. Everything I throw at this MacBook is just a breeze. Never a hiccup. Always snappy. For most of the things, it doesn’t even have to be connected to power. It’s very capable machine and I think Apple did something amazing with the Apple Silicon. It’s just a bit sad to see it’s not used to its full potential, still years down the line since its inception. But I’m trying to be patient.