Can You SLI Two Different GPUs?

GTX 1070 + 980Ti: Two Different GPUs Working Together

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.

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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”.

Types of SLI Configuration

There are three types of SLI configurations in which you can connect multiple GPUs (up to 4).

2-Way SLI – In this, you can connect two single GPU graphics cards in SLI mode using 2-way SLI Bridge.

3-Way SLI – In this, you can three single GPU graphics cards in SLI using 3-way SLI Bridge.

4-Way SLI or Quad SLI – This is also called Quad SLI and in this, you can connect 4 single GPUGraphics Cards in SLI using 4-way SLI Bridge or can connect two dual GPU graphics cards using 2-way SLI bridge. You cannot connect 3 or 4 dual GPU graphics cards in SLI because that would make it Hexa and Octa SLI configuration which does not exist.

Note: 2-way SLI is the most popular and active SLI configuration used today because Nvidia has reportedly dropped most of the support for 3-way and 4-way SLI. This is because of the complexity involved in driver development. Modern graphics cards such as GTX 1070, GTX 1080 and higher will only support 2-way SLI.

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

Also,

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.

Also Read: Does Your PC Need a Graphics Card if its Not for Gaming?

Benefits

The primary benefit of running two graphics cards is increased video game performance. When two or more cards render the same 3D images, PC games run at higher frame rates and at higher resolutions with additional filters. This extra capacity improves the quality of the graphics in games. Most graphics cards render games up to 1080p resolution. With two graphics cards, games run at higher resolutions, such as on 4K displays that offer four times the resolution. In addition, several graphics cards can drive additional monitors.

A benefit of using an SLI or Crossfire-compatible motherboard is that a PC can be upgraded at a later time without replacing the graphics card. Add a second graphics card later to boost performance without removing the existing graphics card. Manufacturers upgrade graphics cards about every 18 months and a compatible card may be difficult to find after two years.

SLI Modes

Nvidia graphics cards will work together in SLI in three main modes: SLI anti-aliasing, SFR, and AFR. You can select and change these modes in the Nvidia Control Panel, which should have been installed onto your computer when you installed your video card drivers.

Split Frame Rendering (SFR)

This method takes the frame that needs to be rendered, analyzes it, and then splits up the frame horizontally into as many pieces as there are cards, and sends the workload between them. It can split the frame how it sees fit based on what’s in the frame.

For example, if the frame contains a mostly empty, static sky in the top half of the frame (less resource intensive), but moving characters in the bottom half (more intensive), then it will determine that one card would be doing more work if it is merely split 50/50. So, the card responsible for the upper portion of the screen may receive about 60% of the screen real estate while the card responsible for the bottom will only have to process the bottom 40%. (Note: these percentages are just vague examples, not concrete numbers.)

Alternate Frame Rendering (AFR)

In this mode, the frames are queued up and each card renders a full-frame. So, if you are running 2 cards, then one would be responsible for even-numbered frames while the other would be responsible for odd-numbered frames. This is often considered more effective than SFR for achieving higher frame rates, but it can also cause issues such as micro stuttering.

Keyword: Micro Stuttering – This it when you see visual stutters on your screen caused by a discrepancy in frame rendering times between cards. If the cards are not synced up properly, or they don’t have enough information to guess the next frame that needs to be rendered, then you will see a delay.

SLI anti-aliasing

This mode allows for better image quality, as opposed to pushing higher frame rates. It works to split the anti-aliasing workload between the cards, increasing the overall quality of your image.

Using this mode can unlock higher anti-aliasing modes within games (such as SLI 8x, 16x, and even 32x on quad-SLI systems).

Keyword: Anti-aliasing – Computer pixels are made of squares, which can result in round images looking jagged around their edges. Anti-aliasing helps fix this by sampling pixels around the problem area and then filling in the best approximate guess.

SLI Bridge Series

BridgePixel Clock SpeedMax BandwidthRecommended Monitor Support
Standard Bridge400 Mhz1GB/s1920×1080 through 2560×1440 @60 Hz
High-Bandwidth Bridge650 Mhz2GB/sUp to 5k and surround sound

If you have more powerful cards (like say the GTX 1080), you can use a standard bridge, but it won’t allow for the full performance of the cards. The high-bandwidth brides would allow for this.

List of Desktop Graphics Cards supporting SLI

Here is the list of all SLI supported desktop graphics cards from Nvidia.

  • GeForce RTX 2080 Ti
  • GeForce RTX 2080 SUPER
  • GeForce RTX 2080
  • GeForce RTX 2070 SUPER
  • Nvidia Titan Xp
  • GeForce GTX 1080 Ti
  • Nvidia Titan X
  • GeForce GTX 1080
  • GeForce GTX 1070
  • GeForce GTX TITAN X
  • GeForce GTX 980 Ti
  • GeForce GTX 980
  • GeForce GTX 970
  • GeForce GTX 960
  • GeForce GTX 950
  • GeForce GTX TITAN
  • GeForce GTX 780 Ti
  • GeForce GTX 780
  • GeForce GTX 770
  • GeForce GTX 760 Ti
  • GeForce GTX 760
  • GeForce GTX 690
  • GeForce GTX 680
  • GeForce GTX 670
  • GeForce GTX 660 Ti
  • GeForce GTX 660
  • GeForce GTX 650 Ti BOOST
  • GeForce GTX 480
  • GeForce GTX 470
  • GeForce GTX 465
  • GeForce GTX 460
  • GeForce GTX 460 SE
  • GeForce GTS 450
  • GeForce GTX 555 (OEM)
  • GeForce GTX 560 Ti (OEM)
  • GeForce GTX 560
  • GeForce GTX 550 Ti
  • GeForce GTX 590
  • GeForce GTX 660
  • GeForce GTX 560 Ti
  • GeForce GTX 545 GDDR5
  • GeForce GTX DDR3
  • GeForce GTX 570
  • GeForce 9800 GT
  • GeForce GTX 580
  • GeForce 9600 GT
  • GeForce 8500 GT
  • GeForce 8600 GTS
  • GeForce 8600 GT
  • GeForce 8400 GS
  • GeForce GTX 275X
  • GeForce GTS 150
  • GeForce GT 130
  • GeForce GT 120
  • GeForce GTS 250
  • GeForce GTX 285
  • GeForce GTX 295
  • GeForce 8800 ULTRA
  • GeForce GTX 280
  • GeForce 8800 GTX
  • GeForce 9800 GX2
  • GeForce GTX 260
  • GeForce 9400 GT
  • GeForce 9500 GT
  • GeForce 9800 GTX
  • GeForce 9800 GTX+

Final Words

In the end I would like to say that I have tried my best to explain all the important things regarding SLI. If you still have any queries or doubts then feel free to ask me by leaving a comment below.

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