Reasonably fast PC but low framerates?

(Mike Childs (TGIF)) #1

Hi, I seem to get fairly low framerates in Zwift. Some days are better than others, but in particular, I participated in a group ride with a few dozen other riders on Sunday morning and the framerate was like that of a powerpoint slideshow for much of the ride. My system runs modern 3d games in higher resolutions and with higher graphics requirements fluidly. My specs are below:


Intel Xeon X5470 (Quad core 3.33Ghz currently at 3.75 Ghz)
Dual nVidia Geforce GTX 460 1GB video cards in SLI performance mode
Video Driver: Latest nVidia reference driver
Power management options disabled for cpu
Power management options disabled for gpu (all on performance mode)
System Memory: 8GB DDR2 PC-6400 @ 800Mhz
480GB SSD SATA3 HD, running at SATA2 due to motherboard. > 100GB free space
Internet: 5Mbps down / 0.5Mbps up
Operating System: Windows 10 Pro - clean install

I have a feeling Zwift might not be taking advantage of my SLI video card configuration? That being said, is a single nVidia GTX 460 1GB not enough to run Zwift optimally? The other games I run appear to be significantly much more graphic intensive and I run them at 1440P, whereas I run Zwift at 720P.

I output Zwift at 720P on to a projector which only supports that resolution, which is why I chose that. I have tried it on my main monitor at normal 1440P resolution and the performance appears to be no different.

Any suggestions?




(Stef Levolger) #2

Zwift leaves something to be desired in terms of performance for the graphics you get in return, that most certainly is true. The game looks decent, but performance wise it’s a bit poor. On the same hardware a graphic intensive game such as Crysis outperforms Zwift in terms of FPS and quality.

Easiest solution is to simply upgrade the GPU. With the increased raw power the performance increases.

(Michael Henasey) #3

I heard that Zwift does not support SLI/Crossfire.

a GTX 460 is below the recommended specs (

try for at least a GTX 950 today. its a lot GPU power for not a lot of money.


(Mike Childs (TGIF)) #4

Thanks for the replies. Is there a guide to modifying the settings files which control the graphics options for the game? I’m happy to play around with them if I can make it run smoother at lower detail for a while. (IE: Disable all Anti Aliasing and unnecessary effects until I can upgrade my video card.

I guess Zwift just isn’t optimized as well as it could be. And I think you are right, the game is using my full 1GB video memory which means it is likely retrieving graphics data from the HDD or system memory causing the problems. I think this could all be ironed out with some deliberate programming to improve how efficient the app runs since many other modern titles can be optimized to run with vastly better in-game graphics with higher framerates and under 1GB VRAM consumption.

I am planning to upgrade my SLI video cards to a GTX 980 Ti single card at some point this year, possibly when the next generation of nVidia cards roll out and the price drops.



(Michael Henasey) #5

This is what I am using while on a Core i3 3.8 GHz, 8GB DDR4 RAM, GTX 950:

res 1280x720(0x) sres 512x512 aniso 4 set gSSAO=1 set gFXAA=1 set gFoliagePercent=1.0 set gLODBias=2 set gHeadlight=0 set gSimpleReflections=1

I play using the High (1080p) in-game resolution. Zwift picks the “high.txt” profile for me. I’m connected to a 40" 1080p 60 Hz LCD TV.

I have also clamped my FPS to 30 using nVidia Adaptive V-sync Half Refresh Rate option. This reduces micro-stuttering to a minimum but does not eliminate it entirely. Zwift is very “playable” and smooth at 30 FPS.

res 1280x720(0x)

I believe this controls the texture resolution, not the in-game resolution (which you control via the Settings screen). The value in parenthesis appears to be the AA value but it does not appear to be implemented.

sres 512x512

I think this is the shadow texture resolution. I set it to as little as possible (take from “basic.txt”).

aniso 4

Anisotropic filtering. Set it to 4 as taken from “basic.txt”. Higher values did not appear to make a significant visual difference in-game. Higher values did not seem to affect my framerate as well.

set gSSAO=1

Screen-space ambient occlusions. You can turn it off by setting it to zero and it will have a large impact both visually and to the framerate. Without it, everything seems dull and flat in Zwift, so I recommend leaving it on unless turning it off is a tradeoff you can live with.

set gFXAA=1

You can’t see to turn off fast approximate anti-aliasing. If you do, Zwift may not display correctly. That was my experience.

set gFoliagePercent=1.0

Reducing “foliage” to something less than 0.5 makes a significant difference in framerate as well as what you see visually.

set gHeadlight=0

I turned off the headlight (gHeadlight=0) because it makes things shine/glare too brightly and it’s distracting to me. It did seem to have a minor framerate effect at times.

set gLODBias=2

set gSimpleReflections=1

Both (gLODBias=2) and (gSimpleReflections=1) are things I took from the “basic.txt” profile and appeared to have an affect on the amount of micro-stuttering I was experiencing. I’m not sure how much of a difference they make visually. I think (gLODBias=2) makes things like other riders models less detailed (e.g. no chain, no cables, etc.) but did not seem to affect my own model/avatar in-game.

All this stuff is based on my interpretation of the settings file and my experimentation. It’s by no means “official” and should not be taken as such.

I too am waiting for GPU prices to reduce and will probably get a 980 or 980Ti.

Good luck!


(Mike Childs (TGIF)) #6

Excellent, just what I needed. Thank you! One more quick question: in the Log file, when it says it picked the “high” setting, does that simply imply the high.txt file?


I backed up the folder containing those settings and am am thinking of just replacing/updating the contents of the high.txt file as I don’t know how to make it pick another settings file.


Also there was a file with a name something like CurrentSettings.txt (going off memory, or something similar). Is that just a record of the previous Zwift session settings I had used, and I should be modifying the high.txt file as that is the one which is read at runtime?




(Michael Henasey) #7

Yes, when the log file says picked “high” that corresponds to the “high.txt” file.

Zwift decides, at run-time, which profile to use, based on your hardware. Unless you change your hardware, or unless Zwift makes some internal changes in the client, you should only have to worry about “high.txt”.

CurrentSettings.txt is an old, left-over file, from the early beta period.


(Mike Childs (TGIF)) #8

Thanks Michael, you have been very helpful.

I look forward to playing with these settings later this evening.



(Jon Mayfield) #9

Make sure you haven’t forced SLI on in the nvidia driver.  With SLI forced enabled Zwift often runs 15-25% as fast as on a single card (yes, its slower on SLI by a lot).  We are not big enough to get NVIDIA to make a proper SLI profile for us, nor can they spend the time to see what in their driver is doing this.

For now make sure Zwift is using a single card - which it will do by default as it does not have an nvidia profile.

(Mike Childs (TGIF)) #10

Thanks Jon, I did force SLI Alternate Frame Rendering in my testing - to no benefit. I will double check it is disabled.