Hello, question!I bought two GeForce GTX 1070 video cards for 38 thousand each and installed them in my computer in an SLI connection, but the results weretests in Futuremark 3DMark show that performance (compared to a single video card) increased by only 10-15%, but I was expecting at least 50%. Also, in modern games, two video cards did not increase my FPS, and in some (in particular FAR CRY PRIMAL) even downgraded. It turns out that it would be better if I bought not two, but one video card for this moneyGeForce GTX 1080 or even GeForce GTX 1080 Ti. And so I threw money away. Please don't repeat my mistake. And yet, few people know that not all NVIDIA tenth series video cards can operate in bridge mode (SLI), for example, the GeForce GTX 1050 and GTX 1060 cannot, either. GTX 1070 cannot be paired with GTX 1080 . Please tell us about this on your website.
Hi all! Almost all users who like to play various games have probably thought or heard about the fact that two or more video cards can be installed in the system to combine their power. Actually, the technology of combining two or more graphics processors for processing three-dimensional images presented by Nvidia is called SLI (scalable link interface, Russian scalable communication interface). The analogue from AMD is called CrossFireX. What are the pros and cons of each technology, is it worth using these technologies, how do they work? This is what I will talk about today.
- And most importantly, I will tell you why it is not profitable for video card manufacturers to have SLI or CrossFireX technologies increase the performance of a computer’s graphics system by 100%.
So let's start with the green ones (Nvidia). In order to add an SLI connection to your system, you will need 2+ video cards of the same series and model. Unlike the red ones (AMD) (which we'll talk about a little later), GPUs are more finicky in this regard. If older lines of cards made it possible to combine absolutely any models into a bridge (the main thing is that they were the same), then in the last tenth line everything changed. You can only build a bridge using GTX 1070, 1080 and 1080Ti. What this is connected with remains a mystery to me personally, but, unfortunately, now only these models can be combined. I can’t give any information about the titans.
(Two GTX 1080 Ti video cards connected by an SLI bridge)
As for the red ones, they have both advantages over the green ones and disadvantages. The main advantage is that you can combine absolutely any models, the main condition is that the video cards being combined are built on the same architecture. For example, AMD allows you to pair the RX 460 and RX 470. But putting the GTX 1070 and GTX 1080 together will no longer work. Well, the main disadvantage of CrossFireX is the performance increase. The power gain when using direct competitor cards for red ones is significantly lower than for green ones. And optimization in most games supporting video card combinations is much worse for AMD. Yes, not all games support SLI and CrossFireX. As for the secondary manufacturer of video cards, it has absolutely no significance. That is, if you have two GTX 970, one from MSI and the other from Palit, then this will not affect the result in any way. This rule applies to both Nvidia and AMD video cards.
To build a system based on SLI and CrossfireX you will need:
1. Motherboard with two or more PCI-express x16 slots that supports this technology. Not all motherboards that have two or more video card slots support a bunch of video cards! There is always a corresponding marking on the motherboard itself, it is written about this on the manufacturer’s website, and it is also always indicated in the accompanying instructions. Remember that if you do not need a motherboard that supports SLI and CrossFireX, then choose the appropriate board, since you will always overpay for the fact that the motherboard is equipped with support for video card communication.
2. Powerful power supply. Two video cards = high power consumption. A unit of 550 watts or more is recommended.
3. The video cards themselves support these technologies.
4. Bridge connecting video cards. As far as I know, AMD allows you to combine cards without using this bridge, that is, using software. However, in this case, the loss in performance will be about 15-20% than if you used a bridge.
In my opinion, it is not worth building a system based on these technologies. But it’s not worth it, because it’s better to buy one more powerful video card than two, but weaker ones. For example, two GTX 1070 will be weaker than one GTX 1080. And all because these technologies have very poor optimization for games and other resource-intensive applications; the green ones are of course better than the red ones, but still bad. The performance gain, as you might think, will not be 100% from using a second GPU. At best it will be 40-50%. And then, in the overwhelming majority it will be 15-25%. That is, the question of the feasibility of such a purchase remains open from a price/performance point of view. It only makes sense to install such a system if the power of the current top-end video card is not enough for you. And this happens only in very highly specialized cases. For example, to achieve a stable number of frames per second on a 144Hz monitor in very heavy games. In light games, the top 1080Ti easily copes with this task. Or if you want to play in high resolution - 4 or 8k.
Also, don’t forget about video memory. If you combine two video cards with different amounts of memory, then only the memory that is smaller in size is used. For example, you installed an RX 480 with 4gb and an RX48 with 8 gb. As you might think, you will have 12 gigabytes of video memory available to you. Unfortunately, it is not. Only 4 gigs will be available. If you have two identical video cards, but operating at different frequencies, then both of them will also operate at the lower frequency. That is, for example, one operates at 1544Hz, the other at 1622Hz, both will operate at 1544Hz. In the future, with a complete transition to DirectX 12, we are promised complete optimization and full use of all resources of the combined video cards. That is, there will be a 100% increase in power and a complete summation of the available video memory. But this is all a promise; in reality, we have what we have. Of course, there are also interesting game projects where we can get 70% or 80% performance gains, but, unfortunately, there are very few of them and they are rather the exception to the rule. As I like to say, it’s ultimately up to you to decide, but I decided for myself a long time ago that at the moment SLI and CrossFireX are extremely impractical!
Why video card manufacturers will never bring SLI and CrossFireX technologies to fruition and why a second video card will never add 100% performance to your computer's graphics system
The answer is very simple. Imagine the situation. You bought a computer with a powerful video card and after a couple of years its power began to not be enough for you. You went to the store or the secondary market and bought an inexpensive second such video card, as a result of which you added 100% performance to the graphics system of your computer. But this will never happen! This is not profitable for the manufacturer, but it is beneficial for you to always buy a new product at an expensive price. That's the whole secret. That's all, see you soon!
Extensiveness and intensity are two key concepts in the development of human progress. Extensive and intensive paths of development of society, technology, and all of humanity as a whole have succeeded each other over the course of many centuries. There are many examples of this in all areas of economic activity. But today we are not interested in agriculture and cattle breeding; we are interested in information technology and computers. As an example, let's briefly look at the development of central processing units.
Let's not delve into the distant 80-90s, let's start right away with the Pentium 4. After a long intensive development of NetBurst technology, increasing the “steroid” megahertz, the industry hit a wall - it turned out to be very difficult to further “overclock” single-core processors and, in order to get more more powerful processor, higher costs required. And then dual-core processors appeared - an extensive solution to the problem. Soon they, too, ceased to provide the required performance, and a new Core architecture appeared, which at lower clock speeds provides greater performance - an intensive solution to the problem. And so it will continue.
But what happens with the development of the second component, which is important for a fan of spectacular games on a PC - the video card? And the same thing happens as with processors. At this stage of development, single-chip video cards can no longer provide the required performance. Therefore, both leading companies in the video card market (NVIDIA and AMD) are developing and actively implementing their own technologies to increase video system performance by combining two, three, or even four video cards in one PC. In this article we will look at the first company (since it was the one that presented its development first) NVIDIA and its SLI technology.
What is SLI technology?
NVIDIA SLI technology is a revolutionary approach to scaling graphics performance by combining multiple NVIDIA graphics cards into a single system.
Story
In 1998, 3dfx introduced the Voodoo2 graphics processor, among other innovations of which was SLI (Scan Line Interleave) technology, which involved two Voodoo2 chips working together to form an image. Even cards from different manufacturers, as well as cards with different amounts of memory, could work with SLI technology. The SLI system allowed working with resolutions up to 1024x768, which seemed incredible at the time. The disadvantages of SLI from 3dfx were the high cost of accelerators ($600) and high heat dissipation. However, soon video cards are moving from the PCI bus to the faster dedicated AGP graphics port. Since there was only one port on motherboards, the production of video cards with SLI support ceased for a while.
In 2000, with the release of the new VSA-100 chip, 3dfx was able to implement SLI on AGP, but this time within a single board that housed two or four such chips.
However, boards based on the SLI system had high power consumption and failed due to power supply problems. About 200 Voodoo5 6000 boards were sold throughout the world, and only 100 of them actually worked. Such an unsuccessful promotion of a promising accelerator, in which very large amounts of money were invested, actually led to the bankruptcy of the company. In 2001, NVIDIA buys 3dfx for $110 million.
In 2004, with the release of the first solutions based on the new PCI Express bus, NVIDIA announced support in its products for multi-chip data processing technology SLI, which stands for something else - Scalable Link Interface (scalable interface).
At first, the advancement of SLI technology did not go very smoothly, primarily due to constantly identified flaws in the drivers, as well as the need to “sharpen” them for each specific application, otherwise the player would not receive any benefit from purchasing a pair of accelerators. But generations of accelerators changed, drivers were improved, and the list of supported games expanded. And so, at the end of 2007, Triple SLI technology was put into operation, making it possible to combine 3 NVIDIA video cards:
The manufacturer promises a performance increase of up to 250% compared to a single chip. But this was not the limit, now Quad SLI is next in line, making it possible to force 4 GPUs to work on visualizing the game scene, albeit as part of a pair of dual-chip video cards.
Imaging algorithms
Split Frame Rendering
Split Frame Rendering algorithm diagram
This is a frequently used mode when the image is divided into several parts, the number of which corresponds to the number of video cards in the bundle. Each part of the image is processed completely by one video card, including geometric and pixel components. ( Analogue in CrossFire - Scissor algorithm)
The Split Frame Rendering algorithm easily scales to 3, 4, and in the future, possibly even more GPUs.
Alternate Frame Rendering
Alternate Frame Rendering algorithm diagram
Frames are processed one by one: one video card processes only even frames, and the second - only odd ones. However, this algorithm has a drawback. The fact is that one frame can be simple, and another difficult to process. In addition, this algorithm was patented by ATI during the release of a dual-chip video card.
Quad SLI technology also uses a hybrid mode, which combines SFR and AFR.
SLI AA (Anti Aliasing), SLI FSAA (Full Scene Anti Aliasing)
This algorithm is aimed at improving image quality. The same image is generated on all video cards with different anti-aliasing patterns. The video card smoothes the frame with a certain step relative to the image of another video card. The resulting images are then mixed and output. Thus, maximum image clarity and detail is achieved. The following anti-aliasing modes are available: 8x, 10x, 12x, 14x, 16x and 32x. ( Analogue in CrossFire - SuperAA)
Construction principles
To build a computer based on SLI you must have:
- a motherboard with two or more PCI Express slots that supports SLI technology (as a rule, the name of the motherboard contains the word SLI).
- A fairly powerful power supply (usually recommended from 550 W);
- GeForce 6/7/8/9/GTX or Quadro FX video cards with PCI Express bus;
- a bridge connecting video cards.
However, we note that support for chipsets for working with SLI is carried out in software, not hardware. But video cards must belong to the same class, and the BIOS version of the cards and their manufacturer do not matter.
Currently, SLI technology is supported by the following operating systems:
- Windows XP 32-bit
- Windows XP 64-bit
- Windows Vista 32-bit
- Windows Vista 64-bit
- Linux 32-bit
- Linux 64-bit (AMD-64/EM64T)
An SLI system can be organized in two ways:
- Using a special bridge;
- Programmatically.
In the latter case, the load on the PCIe bus increases, which has a bad effect on performance, so this method is not widely used. This mode can only be used with relatively weak accelerators.
If the SLI bridge is not installed, the driver issues a warning that the SLI mode will not work at full capacity.
For example, this is what a special bridge for connecting video cards might look like if it is made on PCB. In addition, flexible bridges have now become widespread as they are cheaper to manufacture. But to activate 3-Way SLI technology, only a special hard bridge is used so far, which actually accommodates three conventional ones in a “ring” mode.
As mentioned above, the Quad SLI system is also popularized. It involves combining two dual-chip boards into a single system. Thus, it turns out that 4 chips are involved in creating the image, but this is still the lot of avid enthusiasts and has no practical significance for ordinary users.
For the average user, something else is important, the reason for which this technology was actually conceived. By purchasing a motherboard that supports SLI, you are setting yourself up well for upgrading your PC in the future, as it provides the ability to add another graphics card. No other “upgrade” method, other than a complete system change, even comes close to the increase in gaming performance that a second video card provides.
It looks something like this. You are buying a good PC with a good modern video card. You can easily play modern games, but after a year and a half, your system can no longer satisfy you with the image quality and speed in the latest games. Then, instead of replacing the old video card (or even the entire PC), you simply add another one and get almost double the video system power.
However, everything sounds so simple in theory. But in practice, the user will have to face many difficulties.
The first is the games and applications themselves. No one has yet come up with a cure for the terrible word “optimization” - yes, not only drivers, but also games must be optimized for SLI technology in order to work correctly with it. NVIDIA states that SLI technology supports " longest list of games ». If the game you're interested in is not on the list, the company suggests creating your own settings profile for it.
Unfortunately, there are still a lot of games that are not compatible with SLI, and creating a profile does nothing to fix this. There is only one way out - wait for patches from game developers and new drivers from NVIDIA. However, these games mainly include old ones, which a single modern video card can handle without problems, or less popular ones, which are not interesting to the vast majority of players due to poor “playability”. But new powerful games already provide for the use of two video cards. For example, in the game Call of Duty 4 there is a very specific switch in the graphics settings section.
You can find out that the SLI function is enabled by special indicators right in the game, with the appropriate “test” driver settings.
If you see horizontal or vertical green bars on your monitor screen, this means that the Show SLI Visual Indicators option is enabled in the NVIDIA Display Control Panel. When you enable this option, you can see how the graphics load is distributed on the GPU, and the names of the SLI components in your system will be changed: SLI for two GPUs will be called “SLI”, the name 3-way NVIDIA SLI will be replaced with “SLI x3”, and Quad SLI will be called “Quad SLI”. For games rendered using Alternate Frame Rendering (AFR), the vertical green bar will grow or shrink depending on the extent of the expansion. For games rendered using Split-Frame Rendering (SFR), the horizontal green bar will rise and fall to show how the load is distributed across all GPUs. If the level of detail on the top and bottom halves of the screen is the same, the horizontal bar will be close to the middle. To enable or disable this feature, simply open the NVIDIA Control Panel and select 3D Settings.
The second common problem with computing with multiple graphics chips is synchronizing the latter. As mentioned above, the AFR rendering method has one peculiarity: one frame can be simple, and another difficult to process. If there is a large difference in the complexity of processing a frame, one video card can process it much faster than the second. This leads to “microlags” - small delays in the image, like jerks, but at the same time the overall number of FPS looks comfortable. This effect appears quite rarely, but even the developers don’t know how to deal with it. There is a simple solution for the user - in games where “microlags” are observed with the AFR method, switch to the SFR method, indicating it in the game profile.
In SFR mode, the display is split into two parts. The first card shows the top part of the picture, and the second card shows the bottom. With dynamic load balancing, the driver distributes the load evenly between the two cards.
The third problem is the processor. The fact is that when using several video adapters, the load on the processor increases not only due to the use of heavy graphics modes, but also due to the synchronization of video chips. Therefore, in order to unleash the full potential of a combination of several video cards, you will need a powerful processor. Although today this is not such a pressing issue as it was a couple of years ago.
Additional features of the new technology
The new generation of SLI-enabled motherboards and graphics cards provide users with much more features than conventional 3D graphics acceleration.
Hybrid SLI provides for a more rational use of the mode of sharing the graphics core built into the chipset and a discrete video card.
The technology consists of two parts: GeForce Boost And HybridPower.
The first will be used in applications that intensively work with 3D graphics. With GeForce Boost, part of the calculations of the three-dimensional scene will be taken over by the accelerator integrated into the system logic set, which will give a noticeable increase in performance to those systems that do not have the fastest discrete adapter installed, for example GeForce 8500 GT or GeForce 8400 GS.
HybridPower, on the contrary, will allow the use of integrated graphics, disabling the external accelerator when the user is browsing the Internet, office applications or watching videos. According to NVIDIA, the greatest benefit from this technology will be received by owners of laptops with a dedicated graphics card, whose battery life will significantly increase.
Currently, Hybrid SLI is supported by: desktop GPUs GeForce 8500 GT and GeForce 8400 GS for GeForce Boost; powerful GeForce GTX 280, GeForce 9800 GX2, GeForce GTX 260, GeForce 9800 GTX+, GeForce 9800 GTX and GeForce 9800 GT in HybridPower mode; as well as motherboards for AMD processors based on nForce 780a, nForce 750a, nForce 730a (GeForce Boost function only) with built-in GeForce 8200 graphics accelerator.
As you can see, energy savings can reach impressive values.
A very useful feature for overclockers, since in addition to saving energy, it allows the main video card to “rest” when idle and extend its service life, especially if extreme overclocking is used.
Another useful additional feature of the SLI connection is the ability to use up to 4 monitors simultaneously.
Practical use
We have already repeatedly tested various video cards in SLI mode. Let's try to summarize the information received a little.
When preparing this article, information was used from the official NVIDIA website and the free encyclopedia Wikipedia.
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SLI-Ready memory, otherwise known as memory with EPP (Enhanced Performance Profiles - profiles for increasing performance), was created by the marketing departments of NVIDIA and Corsair.
EPP profiles, in which, in addition to standard memory timings, also “prescribe” the value of the optimal supply voltage of the modules, as well as some additional parameters, are written to the SPD module chip.
Thanks to EPP profiles, the labor intensity of independently optimizing the operation of the memory subsystem is reduced, although “additional” timings do not have a significant impact on system performance.
So there is no significant benefit from using SLI-Ready memory compared to conventional manually optimized memory.
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