View Full Version : Help with SLI :(

30-06-2017, 06:15
Hi guys, can't get SLI working at all with PCars.

GPUs usage sits at < 50% when there are other cars around, but when they leave the scene my usage hits 80-90%.

CPU usage also sits at about 40% the entire time... so framerates are terrible (30-40).

I asked if PCars supported SLI a while ago here (http://forum.projectcarsgame.com/showthread.php?49864-Is-SLI-supported-with-PCars&p=1322015#post1322015), but never got back to answering due to life.

I've been reading through this (http://forum.projectcarsgame.com/showthread.php?22928-SLI-discussion-thread) thread, nothing I've seen has worked so far (tried renaming to AFR-FriendlyD3D, putting everything on prefer max performance, etc).

I have 2x GTX 1080s, i7 6700k, and 16GB of ram. Running on a Acer Preadator X34 (3440x1440).


30-06-2017, 12:28
Hi guys, can't get SLI working at all with PCars.

Technically, it's working. If you have any utilization on both GPU's, SLI by definition is working. The issue is that there is a bottleneck that is keeping them from functioning at a higher capacity. At least what has been reported, unless you increase the resolution (upscale or something similar), that's just the way it's going to be... You have to keep in mind that cards like the 1080 were not on the market when pCARS was in development.

The post in the thread you linked likely has the most information available on the subject. I'll paste it here so you don't have to sort through all the posts:

I would say it has more common with DX11 than with particular platform. Sure with more PCI-E lanes multi gpu work more efficient, but i bet under DX11 overhead is still there.

I didn't test it for months, but now been talking with friend ab. SLI usage in different games here is what i found in pCARS:

-1080p/1440p single GPU usage stay high ar. 96-98%
-1080p/1440p SLI usage drop to ar. 55-70% anytime theres more than one car on track.

Nothing of old tricks help increase SLI load:

-command line like -novr -dx11mt
-lowering settings like grass, reflexion, particles, AA, -skipcrowds
-disabling UEFI options like EIST, eco options, lower state
-adaptive to efficiency in NV panel, disabling g-sync and other options like no. of prerender frames
-with/without overclock
-full screen/windowed
-removing user profile
-clean driver install (DDU)
-same for different tracks+car combo

Clearly there's problem with SLI. The only way I've found to push both card utilization over 90% is significantly increase the resolution with DSR or using extreme downsampling.

Example from my rig: Win X, newest drivers, i7 5960x 4.6GHz + Titan X SLI 1450/8000 MHz

always 20 AIs (no issue with one car remember)

1440p, cards usage ar. 55-70%
average fps gain from single to SLI = 45%

x1.2 DSR cards usage rise a bit
average fps from single to SLI = 63%

x4 DSR cards usage +90%
average fps from single to SLI = 88%

1440p + DS2X cards usage rise a bit
average fps from single to SLI = 65%

1440p + DS9X cards usage +90%
average fps from single to SLI = 89%

03-07-2017, 03:34
Technically, it's working.

Thanks, yes I know that, I mean it's not working properly at all ;)

Thanks for the post, appreciate it. :)