SLI (Scalable Link Interface) is marketed as one of the best things to happen to the gaming industry. However, not as many people take advantage of it as you would expect. SLI might seem like a great option for a newcomer building their first PC, but what exactly does SLI do for gaming, and should you build with it in mind?
If you’re considering a dual GPU setup, you’ve come to the right place.
What Does SLI Do For Gaming?
SLI is an NVIDIA technology that boosts gaming performance by combining graphics cards. Using an SLI bridge, graphics cards can work together on processing each frame to increase efficiency. The resulting performance boost will depend on your GPU and SLI support of the game you’re playing.
There are two main ways in which dual graphic cards work on frames:
- Split Frame Rendering: Here, the workload of rendering a single frame is split evenly between the GPUs. With a two GPU setup, each GPU would work on about 50% of the frame. There is accounting for workload too, so if one part of the frame requires less processing power than the other, the workload on one GPU is increased to even the workload while gaming.
- Alternate Frame Rendering: This type of rendering splits alternating frames between the GPUs. In a two GPU setup, this would mean that each GPU is handling every other frame. However, micro-stuttering could become a problem depending on the game, GPUs, and process efficiency.
Does SLI Help FPS?
SLI can boost FPS on some games. Running a multi-GPU setup will split the workload between both GPUs for games, significantly reducing the time it takes to work on each frame.
The main problem here is that the game you’re playing must have SLI support. Unfortunately, most games don’t. Even years ago, when SLI was new and exciting technology, few publishers built games with it in mind. With few people having multi GPU setups, interest and support for SLI have declined over time.
How Much Does SLI Improve Performance?
SLI could improve performance up to two-fold if used on supported games. However, the performance increase for multiple graphics cards is not linear. Two graphics cards will not always double your performance.
SLI should improve performance in theory. But in practice, it does not always give the performance boost you might expect. For example, a two-GPU setup could increase your FPS two-fold, but a three GPU setup might not give you a threefold increase.
Some games even show reduced performance with SLI setups. This problem sometimes makes it better to play with one GPU even if you have several.
This video from Benchmarks For Gamers on YouTube is a great example:
Unfortunately, if you can’t afford dual graphic cards of the same type, you’re better off going with a single one.
SLI cannot utilize the memory of multiple different cards at the same time. Since all the cards are working on the same task, only the memory from one GPU would be used—the remaining cards would be left to work on performance.
This can cause throttling in high-end cards if you use them with lower-quality cards. The more expensive cards will be forced to work at the same rate as the lowest card in the group.
What Are The Differences Between SLI And Crossfire?
SLI is NVIDIA-based, while Crossfire is AMD-based. SLI is a lot more rigid than its AMD counterpart, requiring you to usually have the same graphics cards if you want to connect them. AMD is less rigid and allows you to link different card types within a particular group.
Another difference is that Crossfire does not require a bridge between the graphic cards, reducing the total requirements you’ll need to run a multi-GPU setup. However, Nvidia’s system is significantly more popular.
Which Games Support SLI?
Although it is becoming less popular, many games still support SLI. Some of the most popular gaming titles offering SLI support include GTA V, Fallout 4, and The Witcher III.
The list of games above work well with SLI. However, many games actually perform worse with an SLI-enabled setup, which explains why SLI is dead in the water right now.
Here are some examples of games that actually perform worse with SLI enabled: Rainbow Six Siege, COD Modern Warfare, Resident Evil 7.
Since not all games perform better with SLI enabled, make sure you do your research before spending the extra money on a second graphics card.
Which Graphics Cards Can You SLI?
You can only use SLI with NVIDIA graphics cards. Although most older NVIDIA cards supported SLI, newer ones are starting to ship without SLI support. The RTX 3080, for example, does not ship with SLI support, although its successor, the RTX 3090, does.
That said, a single 3090 GPU retails at about $2500. Getting two of them for marginal improvements and even lower performance in some games is just not worth it.
If you’re planning to get an SLI setup, the first thing to do would be to ensure that your motherboard is SLI-compatible. Once you’ve determined this, GPU mag has a good list of cards you can use as a guide to picking SLI-compatible cards.
Is SLI Still Worth It?
SLI is not worth it for most people. Unless you have a very large budget or an extra graphics card already, you’ll be better served by taking the cost of multiple GPUs and getting a single higher-quality one, instead.
While the idea is good in theory, SLI lags significantly behind its lofty promises. Cost is the main barrier to SLI technology—a hurdle many cannot get over.
Graphic cards are expensive, especially right now with the ongoing chip shortage. A high-end card like the GTX 3080 retails for close to $2000, and even cheaper options cost around $1000. It’s hard enough to afford one of these, so getting two is almost impossible for most people.
This cost problem is also an indirect cause of the lack of support. Since the technology is not as widely used as it should be, many publishers just choose not to include SLI support for their games.
As big a problem as the cost is, it wouldn’t be such a massive deal breaker if SLI worked the way it was marketed. Nvidia markets SLI technology for bringing “dramatically improved graphics and performance.” This statement is only partially true.
In reality, SLI can work amazingly well on some games and be particularly bad on other games. It depends on support and GPU type, among other factors.
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SLI is a great idea in theory that, unfortunately, does not stick the landing as well as it should. I would generally advise against going for a multi-GPU setup when gaming unless you have the best GPU available.
If you have a low to mid-range GPU, you’ll likely get better results by buying a better GPU than you would from SLI.