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frame rate drop with sli.

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caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
A friend of mine is over and I am helping him setup his car in project cars 2.
with sli "off" at one point on the track I get A frame rate drop from 60 to 56, and it's not awful bad.
with sli "on" I get A drop from 60 to the upper 40's, and it's real awful.
the cards show about 35% usage, the cpu shows about 20% usage at that point, the card clocks are down around 1300 at this point.
What could be going on?
cards, gtx 1080, one is ftw the other is hybrid.
cpu, [email protected].
all ssd's in the rig.
32 gigs, 3000 ram.
 

ShrimpBrime

~MadHatDeLidder~
Joined
Apr 19, 2012
Project Cars 2 does not support SLI. Most benches show similar FPS running a single card.
 

wagex

Chapstick Eating Premium Member
Joined
Jan 14, 2011
its pretty common for SLI to have issues like this in games that it isn't supported, a lot of the time it actually hurts fps when enabled.
 

Dolk

I once overclocked an Intel
Joined
Mar 3, 2008
Frame Rate or Frame Time (not FPS or response time) will drop a certain percentage when using SLI or Crossfire due to the extra hop in communication between the multiple GPUs. People always look at FPS in comparing these types of setups. I've personally tested a few different multi-gpu configs in my system, and I always found that the increase in FPS was not sufficient enough to hide away the loss in Frame Rate. Single card solutions will always win out in Frame Rate.
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
FTFY. :)
Frame Time (not FPS or response time) will drop a certain percentage when using SLI or Crossfire due to the extra hop in communication between the multiple GPUs. People always look at FPS in comparing these types of setups. I've personally tested a few different multi-gpu configs in my system, and I always found that the increase in FPS was not sufficient enough to hide away the loss in Frame time. Single card solutions will always win out in Frame time.

Frame Rate = FPS. Frame Time is what you are talking about and is a known issue with multi-GPU setups...some worse than others (micro stutter).

Good reminder of what it is, but in this case, has nothing to do with the OP. :)
 
Last edited:
OP
caddi daddi

caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
soooooo, I have swung A deal on A pascal titan, I guess that means it goes in the game rig and I build A new rig so the 1080s have A home... what A shame.
I never saw it till my friend played and I could watch the numbers in after burner.
 

Dolk

I once overclocked an Intel
Joined
Mar 3, 2008
FTFY. :)

Frame Rate = FPS. Frame Time is what you are talking about and is a known issue with multi-GPU setups...some worse than others (micro stutter).

Good reminder of what it is, but in this case, has nothing to do with the OP. :)



:-/ Oops, I've had that backwards than for sometime.
 
OP
caddi daddi

caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
I got a snap of afterburner, don't ask for another because I just can't do it again.
with sli enabled it seems to split the workload between the two cards but will not exceed 50% load per card.




crash2.png
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
Because the game doesn't support SLI like was mentioned earlier?

You can try renaming the game .exe to a known game that has a profile and see if that works, otherwise, you have your answer I think, no?
 
OP
caddi daddi

caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
yep, I has my answer to the issue.
there are further questions.
#1, why does the system use both cards but only up to 50%?
why does it not simply load it all on to one card?
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
1. Because it doesn't support SLI
2. See #1. It isn't smart enough to automatically sense it doesnt have a profile and attempts it? Not 100% sure.
 
OP
caddi daddi

caddi daddi

Godzilla to ant hills
Joined
Jan 10, 2012
1. Because it doesn't support SLI
2. See #1. It isn't smart enough to automatically sense it doesnt have a profile and attempts it? Not 100% sure.

the driver or the game or both, because one does and one does not? refering to #2
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
Pictures are worth a thousand words, but not sure what they are saying, here... you disabled SLI?