What Is SLI? Is SLI Really A Life-Saver For GPUs?

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What Is Nvidia SLI

Without any doubt, upgrading a contemporary graphics card is going to put a hole in your pocket. If you’re just looking for the card to upgrade your gaming/streaming quality, there’s something else you’d want to know about.

(Hint: SLI!) Nvidia and its multiple GPU high-tech have come up with a quick fix if you are using an SLI-approved motherboard.

With NVidia’s advancement, the GPU’s processing capabilities are much strengthened. All this translates to getting a stable frame rate without actually spending an extravagant amount.

In this blog, I will be answering what SLI is. We will explore the SLI features. So don’t forget to give it a read till the end.


What Is SLI? How Does It Work?


The acronym SLI stands for Scalable Link Interface. This technology was first put forward by 3Dfx on their voodoo2 graphic card line in 1998. The company was then procured by Nvidia, and the high-tech was laid aside for a while.

Multiple GPU automation made its reappearance in 2004, granting it to work with the present high-tech of PCI-e buses. It is a multi-GPU layout that comes up with intensified turning-over performance.

image of Multi GPU pc
Image Credits: Nvidia

“Multiple GPU” means you can plug in two to four graphics cards of any identical series and model in a row. These are by working on a parallel processing algorithm. It splits the rendering workload equally between the GPUs.

SLI-approved motherboards can perform such tasks. The SLI-approved motherboard are remarkably engineered and possesses multiple PCI X16 slots to operate smoothly.

Plus, the GPU must be connected to at least two PCI notches. SLI bridge connectors are utilized to link them in a row. Once it is customized, suitable drivers are installed. You can validate SLI rendering from the Nvidia control panel.

Despite their similarities, only graphics cards of similar series and models can hook up. Assume that if one manufacturer is MSI and the other is ASUS, a connection would be possible between them. But you cannot connect distinguished cards like GTX 1080 and GTX 1070.


What Are The SLI Modes?


You can choose from three SLI rendering modes available. You can easily select the mode in the Nvidia control panel. It’s your choice. You don’t need a different set of hardware to change modes.

The modes are:

  • Split frame rendering
  • SLI anti-aliasing
  • Alternate frame rendering

Split Frame Rendering (SFR)


The frame that you want to render will be examined by SFR (split frame rendering). Based on 3D complexity, it will be split into many regions and allot these to distinguished graphic cards.

Showing how Split Frame Rendering works in SLI

For instance, if your system has two SLI-configured GPUs, SFR will divide it up vertically or horizontally.

In case GPU 1 starts taking more load as compared to GPU 2, the drivers installed will change the allocation.

In my opinion, this SLI rendering technique is not as advantageous as the AFR mode since some of the work is repeated.

Related guide: What is NVlink? What exactly does NVlink do?


SLI Anti-Aliasing


SLI anti-aliasing gives the appearance of superior quality output, in contrast to SFR, though the frame rate might live through a bit. It doubles the anti-aliasing performance, breaking up the intensive workload for each rendered frame across multiple NVIDIA GPUs.

Infographic of how SLI Anti Aliasing
Image Credits: Nvidia

One device will perform an anti-aliasing pattern that is offset from the regular one, while the other GPU will perform the same stuff in the opposite direction.

Intensive anti-aliasing modes within gaming support 8x and 16x while utilizing two GPUs. On the contrary, when using four GPUs, supplementary mode is 32x, though it is only available for Quad SLI systems.


Alternate Frame Rendering (AFR)


The driver will determine whether to approach the hybrid AFR of SFR. The driver launches groups of multiple GPUs that would divide the workload and then utilizes these groups in AFR. The frames are sequenced, and each card renders a full frame.

Split Frame Rendering SFR

Remember, with split-type; one frame will deal with a lot of GPUs. With AFR, the odd frames would be rendered by the first GPU 1, while GPU 2 would perform the rest of the even part.

To achieve higher frame rates, I believe AFR is more efficient than SFR, but it can also cause issues such as micro-stuttering.


Compatibility And Issues: What Is Needed To Run SLI?


If you have enough slots and you want to take advantage of this SLI high-tech, boosting the system and accommodating the graphic cards will not work. There are a few essentials that need to be met, other than the PCI-E x16 slots.

With SLI, GPU’s RAM matters a lot. For instance, a Geforce GTX 1080 Ti 8GB made by ASUS, another of the exact specs but made by MSI, would work.

Next on the list are the motherboard and power supply. Your motherboard will need PCI-E X16 ports to match the GPUs. Remember that high-end cards use almost 200–350 watts of power, so be aware of it.

Remember that extra GPUs do not equally double, triple, or quadruple RAM because each card has to examine the details at the same time.


What Is The SLI Bridge?


The SLI Bridge is the last thing to remember, but not the least. They are also known as SLI Connectors. You can run two low-end or mid-range cards by using the chipset on the motherboard.

However, when we talk about high-end cards, the chipset does not possess enough bandwidth to run the operations smoothly.

The results will be affected severely. This is where the SLI Bridge comes into action, dividing the data equally to both cards.

SLI bridges are further divided into three parts.

  • Standard bridge
  • LED bridge
  • High-bandwidth bridge

SLI Bridge Series


Standard Bridge:

The pixel clock speed is 400 MHz, and 1 Gb/sec bandwidth. It includes motherboards that support SLI up to 1920×1080 and 2560×1440@60 Hz.

LED Bridge:

The pixel clock speed is 540 MHz. It includes monitors that support 2560×1440 @120 Hz+ and 4K. If the GPU supports intensive pixels, it can also operate on an increased pixel clock.

High-Bandwidth Bridge:

The pixel clock speed is 650 MHz. Nvidia sold it exclusively as it is the fastest one. This includes monitors up to 5K and surround. It is only available in a 2-way configuration.

Graphic cards can be connected in 2-way, 3-way, and 4-way by either using a single bridge or by combining two 2-way bridges. As Hexa and Octa SLI technologies are not yet introduced, it is impossible to combine a 3 or 4-way setup with a 2-way.


The Performance


We are now well-informed of what SLI is and how it works. Would you still speed away to purchasing a powerful GPU? Nvidia claims that twice the cards, double the performance. That is where the water gets a bit murky.

Image of GeForce GTX SLI Setup
Image Credits: Nvidia

The most common complication users face is because most games can’t decide which graphics card to use. Solving this problem is only a developer’s piece of cake, but hardly any developer has that amount of free time.

So, if you’re finding a decrease in the quality of your game after installing the replica of the graphics card, it doesn’t mean there’s a problem with your system. Instead, it’s just an indication that your game isn’t compatible with the SLI mechanism.


List of All Nvidia GPUs That Support SLI


Here is a list of all the Nvidia GPUs that support SLI:

  • 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 etc.

SLI vs NVlink In 2022


NVidia came up with NVlink to achieve better performance. In NVlink, two graphics cards are connected as one for a huge boost in performance. It implies mesh networking, in which every GPU is independent.

Let’s note the properties between SLI vs NVlink. NVlink overcomes the critical flaw of SLI; the slow bandwidth. When NVlink came into existence, SLI high bandwidth could bear only 2 gb/s, while NVlink could go upto 300000 mb/s or 300 gb/s.

The best benefit is we can pool the VRAM in NVlink GPUs. For instance, if two GPUs possess 16 GB rams, their combined memory would be 32 GBS.

Regarding gaming, NVlink can offer a slower FPS, but a handful of modern games provide 2 as 1 GPU.


Final Verdict:

After seeing all of the specifications, functions, and improvements that NVidia SLI offers to its users, I believe SLI is worth the hype. But for the vast majority of gamers nowadays, SLI isn’t a viable option based on characteristics.

Even if you want to play on higher resolutions, you’d be better off investing in a single intensive GPU, which would meet your gaming demands for much less money, brain power, and anxiety than SLI. For most people, SLI will be a waste of money with little return.

However, it does not appear that SLI will go extinct. It may continue to exist for a minority of power players who will benefit from symmetrical graphics cards and are motivated to spend the extra money.


Frequently Asked Questions

#1 – Does SLI increase FPS?

SLI may provide a speed gain, greater display resolutions, and the ability to accomplish more graphics-intensive game features without degrading the game’s frame rate in some graphics-intensive titles.

#2 – What is SLI used for?

SLI is a high-performance technology that enables users to intelligently combine and scale graphics capability by incorporating several NVIDIA GPUs into a single system. SLI scales the geometry and fills rate performance of two GPUs.

#3 – Is SLI good for gaming?

An alternative option for a minority of gamers in the latest gaming style. It hooks up with the concept of being at the heart of multi-GPU technology.

For most gamers today (with smaller investments), SLI is not a good investment with respect to performance.

#4 – Is SLI worth it in 2022?

With all the advanced, powerful GPUs in today’s tech market, going for an SLI is not really a genius approach. I’d recommend you to invest that money in buying one GPU that will be compatible with various games.

#5 – Can two GTX 1080 run 4k?

Certain games, yes; most games, no, if you want to play at high settings. Many games can achieve 4k at 60fps with GTX 1080, but you will have to compromise on game settings.

#6 – What games work with SLI?

A few of the games best scale with SLI are as follows:

  • GTA V
  • The witcher 3: wild hunt
  • Far cry 5
  • Crysis 3
  • Fallout 4
  • Playerunknown’s battleground
  • Dark souls III
  • Diablo III
  • The Elder Scrolls V: Skyrim
  • Tom Clancy’s The Division
  • Call of Duty: Black Ops II
  • Command & Conquer 3: Tiberium Wars
  • Rage

And many more to come.

#7 – Does Fortnite support SLI?

One of the most popular games that does not support SLI is Fortnite. The technology cannot improve Fortnite’s FPS or system performance.

Some users even reported that running Fortnite with SLI enabled caused further troubles, with the game ending up glitching.

#8 – What are SLI requirements?

SLI requires two to four graphics cards of the identical series and model in a row. SLI-approved motherboards will be required to perform such tasks.

Only graphics cards of the same series and model can hook up. Assume that if one manufacturer is MSI and the other is ASUS, a connection would be possible between them.

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