The SLI information guide

[D2ultima]

9 minutes ago, DanielMDA said:

4 years later you are still a legend for maKing this guide. Hope one day you can make a Crossfire Guide

Well thanks. As for a crossfire guide... someone would need to send me a crossfire system. At the moment I'm stuck on a notebook and no AMD cards will slot in because they pretty much stopped making MXM (or any high end parts).

 

I don't mind doing the work, but I refuse to write about this kind of hardware unless I have 1st party access to it. People can tell me all day long they're getting this and that etc, but the minute I ask for proof they have 755000 reasons why going and getting proof is impossible. Then they get pissy if I call them out on it, saying I'm wrong, then when they find out I'm correct they want to drop the subject. So I won't work with others to test (plus I need to be able to see things in front of me on top of this).

 

Not begging or anything, but even if I could afford it right now, there's no point in me buying a full desktop with two AMD cards just to write a guide for it really xD.

[NetworkErrors]

So just purely theoreticly... could i use a evga 780 sc edition 3gb with an evga 780 ti sc edition with also 3gigs?

[TheSLSAMG]

1 minute ago, NetworkErrors said:

So just purely theoreticly... could i use a evga 780 sc edition 3gb with an evga 780 ti sc edition with also 3gigs?

No. The model and VRAM amount have to match to use SLI. The only thing that can differ is the subvendor (EVGA, ASUS, MSI, Gigabyte, etc.)

[Jv2391]

So with my build (I use the Gigabyte 1080) and I got a second one, Would I be able to reduce my screen tearing in 4k and also have at least 60FPS? I keep seeing various understandings of what SLI will do and the various configs it can perform. So I am just trying to have a better grasp on this because while the answers from OP were beneficial I still feel I am lacking understanding of what it actually will do because there seems to be multiple profiles that can perform different things.

[D2ultima]

6 hours ago, Jv2391 said:

So with my build (I use the Gigabyte 1080) and I got a second one, Would I be able to reduce my screen tearing in 4k and also have at least 60FPS? I keep seeing various understandings of what SLI will do and the various configs it can perform. So I am just trying to have a better grasp on this because while the answers from OP were beneficial I still feel I am lacking understanding of what it actually will do because there seems to be multiple profiles that can perform different things.

SLI doesn't really have anything to do with screen tearing. If you want screen tearing to vanish, you can do one of three things:

 

- Use Vsync (heavy input lag, undesirable)

- Use windowed or borderless modes (not supported by all games well, often FAR more stuttery than fullscreen due to terrible coding glares at Black Ops 3 and adds input lag though not nearly as bad as vsync). Windowed/Borderless modes have an extreme tolerance to tearing. It is theoretically impossible to have tearing occur in Windows 8.1/10 because DWM is forced-enabled, but I've seen it happen enough times to know that theories aren't absolute.

- Acquire a gsync monitor and lock your FPS to 56 via a tool like RTSS with gsync enabled. While RTSS DOES add input lag, it will only add lag of 1 frame (negligible realistically) and without hitting the limit for vsync (60fps) you can enjoy Gsync's benefits (no tearing, super smooth) combined with perfect frame pacing unless a game is horribly coded and less input lag than borderless/windowed due to being fullscreen.

 

Profiles can force better scaling and other such things. For example, the Black Ops 3 profile is not good. It loses scaling at higher FPS if you have sufficient GPU and CPU power to push for say... 200 frames (the limit of the multiplayer). The Battleforge profile however fixes this greatly, and improves performance with no visual downsides whatsoever. In other words, it's a "free improvement". But it has nothing to do with frame pacing or tearing. It may have something to do with stuttering, however, which is another thing that the Black Ops 3 SLI profile fixes when changed. You can see someone posted about it here https://forums.geforce.com/default/topic/950887/sli/call-of-duty-black-ops-iii-sli-profile/ and I found out from other 980Ti SLI users later on that it did indeed help their scaling in SLI.

[AngeleJR]

I have a 7700K overclocked to 5 GHz and two GTX 1080s overclocked to 2101 MHz. I also have an Asus ROG Swift PG278Q G-Sync monitor.

I can confirm that microstutters aren't the thing of the past. I definitely still see microstutters in the games that I play. I must be very sensitive to microstutters and this just bothers me.

[Frankenburger]

3 hours ago, AngeleJR said:

I have a 7700K overclocked to 5 GHz and two GTX 1080s overclocked to 2101 MHz. I also have an Asus ROG Swift PG278Q G-Sync monitor.

I can confirm that microstutters aren't the thing of the past. I definitely still see microstutters in the games that I play. I must be very sensitive to microstutters and this just bothers me.

What games?

 

Perhaps there are SLI bits you can switch to that'll help alleviate microstutter.

[D2ultima]

18 hours ago, AngeleJR said:

I have a 7700K overclocked to 5 GHz and two GTX 1080s overclocked to 2101 MHz. I also have an Asus ROG Swift PG278Q G-Sync monitor.

I can confirm that microstutters aren't the thing of the past. I definitely still see microstutters in the games that I play. I must be very sensitive to microstutters and this just bothers me.

Sounds like your system setup, since our specs match and I don't get microstutters unless I'm in a window and media is playing on another screen?

[ekyona]

So I just started a topic and wish I had seen this one. But I have a sli setup of 1080tis and after doing some benchmarks the top GPU held a solid 79-81 c on rise of the tomb raider while the bottom was 60-65. Is that normal temps? Let me know what your guys think. I thought maybe their be a 5-8c difference. First time sli user here. 

[D2ultima]

3 hours ago, ekyona said:

So I just started a topic and wish I had seen this one. But I have a sli setup of 1080tis and after doing some benchmarks the top GPU held a solid 79-81 c on rise of the tomb raider while the bottom was 60-65. Is that normal temps? Let me know what your guys think. I thought maybe their be a 5-8c difference. First time sli user here. 

Normal because your bottom card is blocking your top one's airflow. This is why hybrid cards are useful, and why some people wish for blower cards. Alternately, using an extra motherboard spacing (like slots 1 and 3) and picking a motherboard that will allow multi-GPU in those slots is a decent idea.

 

[ekyona]

There is a one slot space between them both cards. And they are also open air cards. So I guess there is no way I can get it Cooler? Is 78-80c too hot for a GPU? 

[D2ultima]

14 hours ago, ekyona said:

There is a one slot space between them both cards. And they are also open air cards. So I guess there is no way I can get it Cooler? Is 78-80c too hot for a GPU? 

It's not too hot. You may be able to divert air flow to the top card using case fan placement, I don't know. I have never tried to adjust SLI airflow in a desktop setup, but thinking about it, it should be possible.

 

However with Pascal cards that's a significant performance dip compared to sub-60c. So good luck with it. Maybe you could run an AIO setup on the top card, would probably fix any issues (also why I recommend the Hybrid cards for SLI and top end pascal in general).

[ekyona]

5 hours ago, D2ultima said:

It's not too hot. You may be able to divert air flow to the top card using case fan placement, I don't know. I have never tried to adjust SLI airflow in a desktop setup, but thinking about it, it should be possible.

 

However with Pascal cards that's a significant performance dip compared to sub-60c. So good luck with it. Maybe you could run an AIO setup on the top card, would probably fix any issues (also why I recommend the Hybrid cards for SLI and top end pascal in general).

This has helped a lot!! Thank you so much. I kinda got a late start in sli but I want to learn more. I thought I was doing something wrong. With my temps being that hot. 

 

 I have my card cards running at 1950-2000 MHz. I haven’t tried over clocking them. 

 

Before sli I did try to OC my GPU but couldn’t get it stable. I was in 4k reso.  So I most likely was not doing something right. 

[D2ultima]

9 hours ago, ekyona said:

This has helped a lot!! Thank you so much. I kinda got a late start in sli but I want to learn more. I thought I was doing something wrong. With my temps being that hot. 

 

 I have my card cards running at 1950-2000 MHz. I haven’t tried over clocking them. 

 

Before sli I did try to OC my GPU but couldn’t get it stable. I was in 4k reso.  So I most likely was not doing something right. 

No, Pascal cards do not overclock well. I don't expect you to be very good at it as a beginner, if raising the sliders don't work I'd expect most people to give up. I recommend MSI Afterburner or NVIDIA Inspector for overclocking, over Precision X. But if you're in the high 1900MHz range already you should be fine.

[bob112]

I have a gtx 780 ti and have never SLI'ed before I've asked at a couple of forums and generally had a look online and it seems like sli is kinda dying out or support for it is from game developers and NVIDA so i was wondering if you would recommend getting another 780 ti and SLIing them or just getting single 1080 ti?

[D2ultima]

15 hours ago, bob112 said:

I have a gtx 780 ti and have never SLI'ed before I've asked at a couple of forums and generally had a look online and it seems like sli is kinda dying out or support for it is from game developers and NVIDA so i was wondering if you would recommend getting another 780 ti and SLIing them or just getting single 1080 ti?

Neither. bite it until new cards come out, will be soon since OEMs are pretty much touting upcoming notebook cards, and desktop cards are always before that.

 

If 1180 is much better, great. Get one, or an 1170.

 

If it's nothing special, great. Get 1080Ti for cheap.

[Frankenburger]

On 7/10/2018 at 1:02 PM, bob112 said:

I have a gtx 780 ti and have never SLI'ed before I've asked at a couple of forums and generally had a look online and it seems like sli is kinda dying out or support for it is from game developers and NVIDA so i was wondering if you would recommend getting another 780 ti and SLIing them or just getting single 1080 ti?

SLI is far from dying. The notion that "SLI is dying" comes from people who doesn't understand how SLI works, and more importantly, people who don't even own a SLI system.

 

Regardless, buying a second 5 year old card this close to Volta's release is not a good idea IMHO, especially when you consider the 3GB framebuffer is probably going to hold you back in a few modern titles. It would be better to wait for Volta, or if you must upgrade, to get a high end Pascal card.

[szym3k]

Will a TX650M PSU handle 1070ti sli?  Soz if it's a stupid question 

[D2ultima]

57 minutes ago, szym3k said:

Will a TX650M PSU handle 1070ti sli?  Soz if it's a stupid question 

Since 1070Ti cards are about 200W each, as long as your CPU doesn't cross ~150W and your system has some headroom you should be perfectly fine.

 

Won't recommend it for hard overclocking.

[szym3k]

18 hours ago, D2ultima said:

Since 1070Ti cards are about 200W each, as long as your CPU doesn't cross ~150W and your system has some headroom you should be perfectly fine.

 

Won't recommend it for hard overclocking.

So I used the Cooler Master calculator, to see what the power consumption was with my system and 1070ti SLI and it came to around 580 watts, would you say that it's still safe?

[D2ultima]

5 hours ago, szym3k said:

So I used the Cooler Master calculator, to see what the power consumption was with my system and 1070ti SLI and it came to around 580 watts, would you say that it's still safe?

It's enough, it's a 650W PSU is it not?

[szym3k]

12 hours ago, D2ultima said:

It's enough, it's a 650W PSU is it not?

Yeah, its a gold rated 650W from Corsair.

[D2ultima]

7 hours ago, szym3k said:

Yeah, its a gold rated 650W from Corsair.

Right. The TX. It should be fine.

[GamerDude]

Interesting read on possible SLi + Gsync hits in some games, doesn't affect DX12 games though, I wonder what nVidia's spin gonna be on this:

https://www.extremetech.com/extreme/279259-nvidia-gpu-performance-craters-when-g-sync-sli-are-used-together

[D2ultima]

17 hours ago, GamerDude said:

Interesting read on possible SLi + Gsync hits in some games, doesn't affect DX12 games though, I wonder what nVidia's spin gonna be on this:

https://www.extremetech.com/extreme/279259-nvidia-gpu-performance-craters-when-g-sync-sli-are-used-together

Gsync requires more bandwidth from SLI, so it would negatively affect scaling, and on x8/x8 systems it would knock some games into more unfavourable or even negative scaling if they were otherwise borderline or already low scaling situations.

 

DirectX 12 doesn't use SLI for any games yet (though bits DO exist, just unused) and thus are using just the PCI/e bus for multi-GPU, and handles things in a different manner. I don't know the specifics because it's a per-game situation, though, but it's possible the render type or how it's using the second card is not as affected by bandwidth.

 

*clicks link*

 

lmao lovely detection skills. The SLI/Gsync perf drop is indeed present but Octiceps was talking about 411.xx drivers being completely broken for gsync... it's a single GPU test. I talk to the dude all the time.

 

 

That said, the rest of the article rings true... it's using x8/x8 lanes because mainstream CPU, so little bandwidth.