Are you building a custom gaming rig and are unsure about whether can you SLI two different GPUs, then here we will try to dispel your concerns.
For starters, know that SLI is a technology that is used by NVIDIA for its multi-GPU setup. The AMD counterpart for SLI is Crossfire.
So the simplest answer to the question whether you can SLI two different NVIDIA GPUs is NO! You cannot SLI two different NVIDIA Graphics Cards. NVIDIA is very inflexible in this regard.
AMD Crossfire, on the other hand, offers some flexibility in terms of the GPUs that you can pair.
However, there are a few other very important aspects about NVIDIA SLI that you MUST learn before you continue building your custom rig.
Here we explore the concept of SLI in depth and also talk about whether SLI is still relevant.
FYI; What is SLI Technology?
SLI is a Multi-GPU technology used by NVIDIA. This is worth noting especially for those who confuse the term “SLI” as an umbrella term for AMD multi graphics cards technology as well.
AMD multi graphics card technology is known as Crossfire.
SLI practically allows 2x improvement in performance when used right. However, whether a game supports multiple GPUs or not depends on the drivers installed and NOT on the game.
The NVIDIA drivers dictate whether a certain game would support SLI or not. If a particular game doesn’t yet support SLI, you can pray that the next driver update would bring with it the SLI Profile for that game, however, there is no guarantee (in fact NVIDIA would no longer release SLI profiles for any future games, more on this below)
In other words, not all games support SLI.
Can You SLI Two Different GPUs?
Simply put, NO! you cannot SLI two different NVIDIA graphics card. In order for SLI to work, you need to have GPUs with the same chipset.
For instance, an NVIDIA GTX 1070 can only SLI with another NVIDIA GTX 1070 only. Similarly an RTX 2080 can only SLI with another RTX 2080.
Does It Have to Be from the Same Brand?
No! In order to SLI NVIDIA graphics card, they do not need to be of the same brand. As long as they have the same chipset, they are good for SLI.
For instance, an EVGA GTX 1660 CAN SLI with ASUS GTX 1660 since they have the same GPU chipset “1660”.
Do You Need to Have Same VRAM?
Ideally, YES! When getting graphics card for SLI, you should aim to get two with the same VRAM amount. Otherwise, while the SLI WILL work, it will operate with capacity of the lowest of the two.
For example, if you get an NVIDIA GTX 1060 3GB VRAM GPU and an NVIDIA GTX 1060 6GB VRAM GPU for your SLI setup, then while the SLI WILL work, it will only work at the reduced performance of 3GB each.
In other words, the VRAM will NOT add up here to 9 GB, instead, it will be brought down to 6 GB in total.
Does “Ti” Matter? Can You SLI “Ti” with “Non-Ti”?
Some NVIDIA graphics card have the “Ti” suffix. This stands for “Titanium” and basically says that the particular graphics card is more powerful than the vanilla version.
For instance, the NVIDIA GTX 1660 has both non-Ti as well as Ti version. So can you install an NVIDIA GTX 1660 with an NVIDIA GTX 1660Ti?
No! Unfortunately, you cannot SLI Ti GPUs with non-Ti GPUs. They are NOT the same GPU chipsets!
Is SLI Dead? – DirectX 12; a Death Knell for SLI?
Recall from earlier in the article where I mentioned that whether a game supports SLI or not is determined whether NVIDIA has released a driver profile for it.
Well that is how it was until very recently with the release of DirectX 12 and Vulkan APIs.
Now. instead of relying on NVIDIA to release the SLI profiles for a certain game – which are often buggy and not made to squeeze out the best of the performance from the multiple GPUs – with DirextX 12 and Vulkan graphics API, the game developers can now write their own codes to make use of multiple GPU in the best way possible.
In a popular press release by NVIDIA titled “NVIDIA SLI Support Transition to Native Game Integrations“, they mentioned:
NVIDIA will no longer be adding new SLI driver profiles on RTX 20 Series and earlier GPUs starting on January 1st, 2021
For GeForce RTX 3090 and future SLI-capable GPUs, SLI will only be supported when implemented natively within the game.
The ability for the games and applications to control if and how they support multi-GPUs is called Explicit Multi-GPU support. Here is a comprehensive article on this topic.
In all reality, NVIDIA pulling out of creating SLI profiles and putting this burden on the developers shows the waning popularity of the SLI and multi-GPU itself.
This along with the fact that all, but the RTX 3090, from the RTX 30 series (i.e the RTX 3070 and the RTX 3080) lack an NVLINK connector indicate the end of the SLI era is nigh.
What Can You Do with Your Second NVIDIA Graphics Card?
It should be clear by now that if two NVIDIA cards are NOT the same, you cannot SLI them.
So what can you do if you have a spare NVIDIA graphics card laying around. Well other than selling it off, you can actually install it for a few uses.
1. Set it Up for NVIDIA Physx
If you want to improve your gaming performance, on certain games, especially on older titles, you could setup your second card as a dedicated PhysX card. You can set a particular card as a dedicated PhysX card via the NVIDIA control panel.
What is Nvidia PhysX?
As the name suggests, NVIDIA PhysX is a critical physics related engine. It was fairly popular a decade ago, however, its relevance has somewhat diminished recently with only a handful of latest games supporting hardware accelerated PhysX.
For a complete list of PhysX supported game, visit this page.
VolnaPC.com actually conducted a study on whether a PhysX card can improve the gaming performance or not. The study is outdated, but for the games that do support PhysX it is still relevant.
Here are the results:
There is a clear improvement in performance.
However, pairing an old GPU for PhysX with a new powerful GPU can in fact damage the performance. The older GPU can bottleneck the newer high performing graphics card.
You will need to test and benchmark the performance difference with and without a dedicated PhysX card.
How To Enable PhysX
Enabling a dedicated card for PhysX is fairly simple.
- Open NVIDIA Control Panel
- Select “Set PhysX Configuration” from the panel on the left.
- Select the drop down menu under the “Select a PhysX processor” to find your dedicated PhysX card.
Note that if you have none installed as a dedicated PhysX card, then your CPU will be the default PhysX processor.
Is PhysX Still a Thing?
As mentioned earlier, it should be noted that hardware accelerated (GPU-based) PhysX support is rarely seen on games these days. Modern GPUs and CPUs are well equipped to handle the PhysX related operations in games.
Contrary to popular belief, PhysX is not dead. It is in fact the integral part of most latest gaming engines like Unreal 4, Frostbite or the Unity 3D. Its just that the Hardware Accelerated or GPU based PhysX games are rarely made.
So in short, if you have a spare NVIDIA graphics card at your disposal and since you cannot SLI it UNLESS both of your GPUs have the same chips, then dedicating it as a PhysX based card is still worth a try.
You can test the frame rate before and after installing a dedicated PhysX card.
Also Read: Does Motherboard Matter for Gaming?
2. Mining and SLI Configuration
While not as lucrative as it used to be, you can use your second NVIDIA graphics card for crypt0-mining.
Therefore, you can earn some cash in the background.
However, this would only be viable if the rate at which you make money mining is higher than the electricity cost of running that second GPU.
Also Read: How to Connect Extra Fan to Motherboard?
Installing a second CPU is not a matter of just slapping in a new graphics card on an available PCIe slot.
The first thing you will need to make sure is if you have enough PCIe lanes to support dual graphics cards.
Secondly, you will need to make sure that you have a Power Supply Unit powerful enough to support the requirements of the two graphics cards optimally.
Lastly, you will need to have an excellent ventilation system to remove the heat generated by two graphics cards.
SLI is a bit draconian when it comes to their multi-gpu compatibility so the answer to the question can you SLI two different GPUs is NO, you cannot.
However, you CAN put your second graphics card to good use if you have an available PCIe slot left.
Also, when looking into SLI, it is also worth checking out SLI compatibility of the games you want to run since not all games are supported.