Content of the material
- Major Requirements of SLI or Scalable Link Interface
- Identical SLI Graphics Cards
- SLI Motherboard
- SLI Bridge
- Operating System
- SLI Driver
- Powerful Power Supply
- SLI Games & Applications
- How CrossFire works
- How to Install and Setup SLI
- Build Your Own PC
- What’s the difference between SLI and CrossFire?
- How does SLI work?
- How Much Faster is SLI for Gaming?
- The Pitfalls of Using Multiple Graphics Cards
- Is SLI or CrossFire right for me?
- Compatibility and Issues
- Two (or more) of a Kind
- Slots and Plugs
- Seeing Double
- What is the SLI Bridge?
- Causes of Do SLI cards have to be identical???
Major Requirements of SLI or Scalable Link Interface
The major requirements for running an SLI configuration are as follows:
Identical SLI Graphics Cards
The first and foremost requirement of SLI is two or more identical SLI Ready Graphics Cards. This means these graphics cards should have the same GPU and Memory capacity. For example you can run two GTX 1070 graphics cards in SLI but you can’t run a GTX 1070 and GTX 960 in SLI mode. You can use graphics cards having the same GPU from different manufactures in SLI e.g. you can use Asus GTX 1070 with EVGA GTX 1070 or other GTX 1070 from the different graphics cards manufacturer.
The other major requirement of SLI is the SLI enabled motherboard. A motherboard that supports SLI comes with two or more (up to 4) PCI Express x16 slots and it is specified on their product detail / manual or on their web page that it is SLI Ready or SLI Certified. This is because all motherboards having multiple PCI-Express x16 slots do not support SLI. Some motherboard supports SLI, some CrossFire (AMD multi-GPU technology) and some can support both SLI and CrossFire. Most of the Z series motherboards support SLI.
For Dual GPU Graphics Cards you don’t need SLI motherboard as they can work in SLI mode on normal motherboards too having PCI-E x16 slot.
SLI Bridge or SLI Connector is a small connecting device or connector that connects two or more SLI graphics cards. It plugs in the SLI slots of your graphics and establishes a direct connection or communication between two or more graphics cards for data transfer. It is much faster than the PCI Express Bus and offers much higher bandwidth.
It is possible to run graphics cards in SLI mode without SLI Bridge but then the performance will suffer especially in the case of high-end graphics cards that offers greater bandwidth.
There are three types of SLI Bridges:
Standard Bridge – It runs at 400MHz Pixel Clock and offers 1GB/s bandwidth. This is the most basic and common type of SLI bridge and comes with motherboards that supports SLI. It is recommended for monitors up to 1920×1080 and 2560×1440@60Hz.
LED Bridge – This Bridge has higher performance compared to Standard SLI Bridges. It has Pixel Clock of 540 MHz and is recommended for monitors up to 2560×1440@120 Hz+ and 4K. It is sold by Nvidia, EVGA, MSI, Asus and other graphics card manufacturers.
High-Bandwidth Bridge or SLI HB Bridge – This is the fastest SLI Bridge and offers maximum Bandwidth. It has 650 MHz Pixel Clock and supports monitors up to 5K and Surround. SLI HB Bridges are available only in 2-way configurations and are sold only by Nvidia. Supported graphics cards include GeForce GTX 770, GTX 780, GTX 780 Ti, GTX 970, GTX 980, GTX 980 Ti, GTX 1070, GTX 1080 and GTX TITAN series.
SLI configuration won’t run on operating systems that do not support SLI. Operating systems that fully support SLI are given below:
- Windows Vista 32-bit
- Windows Vista 64-bit
- Windows 7 32-bit
- Windows 7 64-bit
- Windows 8 32-bit
- Windows 8 64-bit
- Windows 10 32-bit
- Windows 10 64-bit
Also you require 2GB to 4GB RAM (for 64-bit OS) for SLI.
As of now you do not have to download special drivers for SLI because NVIDIA ForceWare Unified Driver Architecture (UDA) supports SLI technology. You just have to download the latest driver for your graphics card as all the SLI profiles and SLI drivers comes include in it.
Powerful Power Supply
You need a very powerful and reliable power supply if you are running two or more high-end graphics cards in SLI mode on your computer. This is because each high-end graphics cards can consume up to 200 – 250 Watts of power which results in tremendous power requirements altogether.
SLI Games & Applications
All games and applications do not support SLI technology. You can only see performance increase in games and applications that are GPU bound and supports multi-GPU configuration. For them Nvidia includes SLI profiles in their driver package so that you don’t have to configure anything for them. Almost all the latest games support SLI and you can really increase your gaming performance to much greater level.
How CrossFire works
CrossFire again has a master card that calls the shots. Overall it works very similarly to SLI, with the key difference being how the workload is divided.
CrossFire divides each frame into a "checkerboard" pattern. Imagine a checkboard of red and black squares superimposed over your monitor. In a 2-GPU CrossFire system, one GPU would render all of the red squares and one would render all of the black squares (so that they are each rendering every other square). In a 3-GPU system, each GPU would render every third square. In a 4-GPU system, 2 GPUs would each render half of the red squares, and the other two would each render half of the black squares.
Again, all data passes back to the master to be combined and sent to the monitor.
How to Install and Setup SLI
The actual physical installation of SLI is very simple, and just a matter of installing GPUs in the right slots and attaching the SLI bridge between them. The potentially difficult and time-consuming part is the software side of things, and getting certain games to run smoothly without issues such as visual glitches/micro-stuttering (even in games that do support SLI).
For more exact detail on installing a SLI setup, see the video below, but here are the quick overall steps on how to set up SLI in a nutshell:
- Install GPUs into PCIe x16 slots on the motherboard, referring to the motherboard manual for guidance on which slots to install them in (and considering maximum airflow, too).
- Connect power supply PCIe connectors to all the graphics cards.
- Attach a SLI bridge on top of the cards.
- Connect the DisplayPort/HDMI cable to the card installed at the top of your motherboard
- Enable SLI in the NVidia control panel in Windows
Build Your Own PC
By Brent Hale
By Jacob Fox
By Robert Brandon
By Jacob Fox
What’s the difference between SLI and CrossFire?
SLI works only with Nvidia GPUs, but AMD has its own multi-GPU technology, called CrossFire, that works in much the same way. CrossFire has the benefit of being a little more flexible with the cards that can pair up with each other, generally allowing CrossFire between cards within the same series.
Some other differences crop up in the way SLI and CrossFire handle multi-monitor setups; CrossFire allows monitors of various resolutions, whereas SLI is limited to two monitors with the same resolution. However, games aren’t forced into full screen the way they are with CrossFire. Overall, CrossFire is a slightly more flexible alternative for AMD multi-GPU systems.
How does SLI work?
Having two GPUs gives your system more rendering power by splitting the task between the cards. One card renders part of the image, and the other processes the rest.
This can be split horizontally along the screen, but there are other methods for assigning rendering duties, like processing alternate frames. The GPUs communicate across a special connector called an SLI bridge rather than through the PCIe ports on the motherboard.
How Much Faster is SLI for Gaming?
So how much better is having multiple video cards for gaming? In theory, having multiple video cards sounds amazing, but in reality it doesn’t quite pan out the way you perhaps had thought. Having multiple GPUs doesn’t scale performance linearly when it comes to gaming, which basically means that SLI won’t give you double the gaming performance.
In fact, in most games that support NVidia SLI, the performance scaling isn’t anywhere near linear. In other words, you’re not even going to get close to doubling your performance in the majority of games that are supported by SLI. Exactly how much faster SLI is compared to a single graphics card varies a lot from game to game and setup to setup. On one hand, the games that scale the best using SLI may net you an extra 50-80% extra performance vs a single GPU. But on the other less-appealing side of the spectrum seeing a disappointing 10-50% boost in frame rate is a very common scenario in many SLI-supported games. In the worst case scenario, which does happen believe it or not, certain SLI-compatible games may even reduce your performance in certain configurations. SLI these Star Wars themed Titans like Linus did and you have my respect
This generally poor scaling is one reason why building a SLI PC is definitely not for everyone, and absolutely not for anyone seeking value for money and/or looking to be cost-effective. Furthermore, even if a game scales okay and does end up providing 50-80 percent higher frame rates, in some games it’s possible to encounter visual artifacts/glitches or a phenomenon referred to as micro-stuttering (caused by inconsistent or spikes in frame times) which can hinder the smoothness of your gaming experience and make SLI not worth it for that particular game (if you can’t find a way to fix it that is, as there are workarounds you can find online).
The Pitfalls of Using Multiple Graphics Cards
While utilizing multiple graphics cards has been a great way to help users get more in-game performance out of their systems, in recent years, the performance advantage of running SLI or CrossFire systems has diminished slightly.
In the past, more game developers took the time to develop their games to be compatible with multi-GPU technology. Nowadays, though, fewer developers are working to optimize their games for SLI and CrossFire configurations.
Still, though, running dual GPUs can provide a nice increase, with many benchmarks showing ~50% higher improvements when adding a second card.
Questions do surround the future of dual-GPU setups, though. NVIDIA themselves have even pulled back on SLI support on a few of their latest generation cards. Only the GTX 1070 or higher can be SLId. The GTX 1060 can technically be set up in multi-GPU configurations, but it is not officially supported by NVIDIA (they have not included the SLI connection ports on 1060s).
Another downside of running SLI or CrossFire setups is the costs involved make them a tough buy for anyone that has any kind of restrictions on their budget.
While one could argue that since dual GTX 1070s cost only slightly more than a single GTX 1080 Ti and often outperform a single 1080 Ti in benchmarks, that they offer a similar (or better) price-to-performance. However, the reality is that dual GTX 1070s will require you to spend more money on your power supply, motherboard, and your case/cooling. This is because dual graphics cards will produce more power consumption and heat, and will also require an SLI certified motherboard (which are typically more expensive) as well.
So, you have to factor in those extra costs when determining the price-to-performance of running multiple cards.
Is SLI or CrossFire right for me?
If you absolutely must have the best performance that money can buy today, then these are technologies intended specifically for you. Go hog wild.
Most people have a budget, though. For them it is not such a clear proposition. Combining multiple cards does provide more performance, but the gains are not huge and not universal. Two of today’s top-end cards put together will perform roughly as well as a high-end card from the next generation, assuming past trends hold. But the two cards cost more overall (if you buy a card today and a next-gen card down the road, you can sell the first card to help finance the second one), consume more power (with rare exceptions), and generally not offer a performance advantage.
Others plan to buy a mid-range card, and down the line (once prices fall) add another mid-range card like it. This yields performance comparable to a single high-end card from the same generation, typically. Performance that is not too far above a mid-range card from the next generation. As before, the possibility of selling the old card to finance a new one makes it hard to justify two cards on a cost basis.
And some people think it very clever to buy up two very cheap cards, stick them together, and have a cheap solution for great performance. In practice these set-ups often perform terribly, and don’t even touch a single, mid-range card of the same generation… or even one generation older.
Compatibility and Issues
Alright, so all you need to do is buy two graphics cards? Do I just slap any two Nvidia cards into my motherboard and call it a day? Unfortunately, it’s not that simple. But then again, it never is…
Two (or more) of a Kind
The first thing you need to know is what graphics cards will pair together; not just any two cards will work. They have to be the same GPU, and they have to have the same amount of video RAM.
For example, if you had a GTX 1070 TI 8GB made by Asus, and another of the exact same specs, but made by MSI, it would still work. A GTX 1070 and a GTX 1080 are not compatible, as they are not the same GPU.
You will also need to make sure that the graphics cards are SLI compatible themselves, as cards without the SLI port on top may not be compatible. Also, it is worth noting that Nvidia killed support for 3 and 4 card SLI for the GTX 10 series.
Slots and Plugs
Next on the list is your motherboard and power supply. These will both need to be SLI compatible.
This means that your motherboard will need enough PCIe x16 slots to match your number of GPUs and your power supply will need enough PCIe connectors to power the amount of cards you will be using.
A common misconception about SLI is that you can get double, triple, or even quadruple video RAM with more graphics cards. Unfortunately, Nvidia SLI only uses the RAM from one card, as each card needs to access the same information at the same time.
What is the SLI Bridge?
The last thing you will need in order to run your SLI setup is an SLI bridge. Nvidia uses a physical connector to bridge the graphics cards together, allowing them to communicate with each other without using precious bandwidth on the PCIe slots.
You will need one of two SLI bridges: either the standard bridge (for less powerful cards), or a high-bandwidth bridge (for the more powerful cards).
Causes of Do SLI cards have to be identical???
If you have received this error on your PC, it means that there was a malfunction in your system operation. Common reasons include incorrect or failed installation or uninstallation of software that may have left invalid entries in your Windows registry, consequences of a virus or malware attack, improper system shutdown due to a power failure or another factor, someone with little technical knowledge accidentally deleting a necessary system file or registry entry, as well as a number of other causes. The immediate cause of the "Do SLI cards have to be identical??" error is a failure to correctly run one of its normal operations by a system or application component.