3 Parts: Installing CardsSetting the SLI ModeTesting Performance

If you like playing computer games, you probably want your games to work as well as possible. One of the key features game computer  - this is his video card; In the case of the Nvidia manufacturer, you can connect two or more identical video cards together to get a huge performance boost. Follow our advice to learn how to do this.

Steps

Part 1 of 3: Installing maps

1. 1 Make sure your operating system  supports SLI technology.  Two SLI cards are supported windows systems  7, Vista, 8, or Linux. Three and four SLI cards are supported only in Windows Vista, 7 and 8, but not on Linux OS.
2. 2 Check the installed equipment.  SLI technology requires a motherboard with multiple PCI-Express slots, as well as a power supply with enough connectors. You will need a power supply unit that provides at least 800 watts of power.
   • Some cards allow parallel operation of four video cards in SLI mode. Most cards are made for working in the mode of two video cards.
   • The more video cards, the more power is required.
3. 3 Take video cards that support SLI technology.  Almost any modern Nvidia card supports SLI configuration. To do this, you need at least two identical models of cards with one amount of video memory.
   • Cards do not have to be produced by one manufacturer, it's enough that they are the same models with an equal amount of memory.
   • Cards do not have to have the same frequencies, but then you can see a slight drop in performance.
   • For best results, use identical video cards.
4. 4 Install the video card.  Install the cards in two PCI-Express slots on your motherboard. Graphics cards are installed in slots in the usual way. Try not to damage the mounts, or do not install the cards at the wrong angle. Once the cards are in place - secure them with special fasteners, or screws.
5. 5 Install the SLI bridge. All cards that support SLI mode are usually shipped with a special "bridge" SLI. This connector connects to the top of the video cards, thus connecting them together. This allows the cards to transfer data to each other directly.
   • The bridge does not have to be installed to connect cards in SLI mode. Without a bridge, the cards will work together using PCI-Express slots on the motherboard. This type of connection will lead to reduced performance.

Part 2 of 3: Setting the SLI Mode

1. 1 Turn on your computer.  After installing the video cards, close the computer case and restart it. You do not need to make any changes to the settings until the system is fully turned on.
2. 2 Install the drivers.  Your operating system should automatically detect graphics cards and try to install suitable drivers for them. This process may take longer than installing graphics cards, because the drivers will be installed separately for each card.
   • If the installation does not start on its own - download the latest drivers from the Nvidia website and run setup files  at the end of the download.
3. 3 Configure the SLI.  Once the drivers are installed - right-click on the desktop and select "Nvidia Control Panel". A new window opens where you can change the graphical settings. Find the menu item named "Configure SLI, Physx".
   • Select Maximum 3D Performance and select Apply.
   • The screen will blink several times while the SLI settings are applied. You will be asked if you want to save the new settings.
   • If there is no function in the control panel, then your system probably did not recognize one or more of your cards. Open the Device Manager in the Control Panel and verify that all graphics adapters  are present in the list of Video adapters. If your video cards are not in the list - check the connection, as well as the installed drivers.
4. 4 Enable SLI technology.  Select Change 3D settings from the menu on the left. In the general settings, scroll down the list until you find the "SLI Performance Mode" parameter. Change the parameter from "One GPU" to "Alternative Processing 2". This way you enable SLI mode for all your applications.
   • You can make separate settings for different video games by opening the Application Settings tab and selecting "SLI Performance Mode".

Part 3 of 3: Performance testing

1. 1 Check the number of frames per second.  There are many different waysto know the number of frames per second, so you will need to choose the most suitable one. The number of frames per second will perfectly show the performance of your system, as well as whether everything is handled correctly. Many fans of computer games achieve a performance of 60 frames per second at high settings.
2. 2 Turn on the indicator sLI work.   In the Nvidia control panel, open the "3D Settings" menu. Enable the function "Display SLI work indicator". You will have a bar on the left side of the screen.
   • Run your game. Once your game is launched, you will see how the bar changes. The strip will be higher - that means the performance has increased, which means that the graphics cards work correctly in SLI mode, improving the display. If the strip is not too high, then the SLI configuration does not greatly affect the overall performance.

Finally, we waited! At least, those users who are not enough for one graphics card today. What difference does it make how much this solution costs if it provides an unsurpassed speed in the highest resolutions with the maximum level of detail. Finally, nVidia was able to present a working realization sLI technology. The concept of SLI is familiar to us for a long time: two video cards working in parallel - remember the old Voodoo2 cards from 3dfx? Although nVidia is also called SLI, its implementation is somewhat different.

Revival of the principle of using two graphics cards  It became possible due to the appearance of the PCI Express interface. Having released the nForce4 chipset, nVidia was the first to introduce the PCI Express platform, which corresponds to the task. For more information, please see nVidia implements SLI: the power of two GPUs in one computer .

Collecting components for the SLI system is easy: you need to find two identical cards nVidia GeForce  6800 Ultra, 6800 GT or 6600 GT with support for PCI Express, as well as SLI-compatible motherboard  on the nForce4 SLI chipset plus a bridge for connecting two cards. Usually this bridge manufacturers of motherboards are enclosed in the delivery set. Since manufacturers often change the distance between two x16 slots, some bridges allow you to adjust your length.

For SLI, nothing else is needed - except for the money that will have to be paid for all this economy. The fact is that the motherboard with SLI support will cost you much more than the usual version, not counting the cost of the second video card. Also, you should get a powerful power supply with a 24-pin plug. Owners of LCD monitors can also have problems. The fact is that most displays have a "native" resolution of 1280x1024. However, the performance potential of the SLI system on two GeForce 6800 cards today can only be revealed in a resolution of 1600x1200. If you reduce the resolution, the CPU bottleneck will be the bottleneck, so you will have to spend money on a more powerful processor.

In general, the SLI system is not cheap. In the next sections of this article we will share our experience and test results of the first motherboards with SLI support from ASUS and MSI.

At the moment, nVidia offers three different modes for SLI.

• Compatibility Mode.
• Alternate Frame Rendering (AFR).
• Split Frame Rendering (SFR).

In compatibility mode, only one card of the two works. There is no performance gain. In AFR mode, one of the computer cards produces all even frames, and the second card - all odd. That is, the rendering is divided between two cards in frames.

In SFR mode, the display is divided into two parts. The first card gives the top of the picture, and the second - the bottom one. Due to dynamic load balancing, the driver evenly distributes the load between the two cards.

nVidia explains in some detail the specifics of SLI mode rendering in two tutorials (in English): GPU Programming Guide  and SLI Developer FAQ .

For our SLI test, we obtained from NVIDIA two reference cards GeForce 6800 Ultra and 6800 GT with PCI Express interface. Outwardly these cards differed only in the size of the radiator. Both models are equipped with two DVI-I outputs (VGA output is provided via an adapter) and a TV-out. As usual in the case of PCI Express cards, the PEG power connector (PCI Express Graphics) was located on the back of them. Since such connectors are equipped only with the latest power supplies, you may need adapters.

Unfortunately, we were not able to quickly find two SLI-compatible GeForce 6600 GT cards, because the two card models in our lab did not support SLI, despite the suitable connectors.

Configuring SLI on nVidia GeForce 6800 Ultra cards.

Configuring SLI on nVidia GeForce 6800 GT cards.

The SLI configuration on nVidia GeForce 6600 GT cards did not work.

Without a bridge, SLI is indispensable here. At motherboards the distance between graphic cards is clearly set. All motherboard manufacturers specify a different distance between the x16 slots, so they attach the appropriate bridges to the package. We got two adjustable bridges from nVidia, which cover any desired distance.

Different SLI bridges.

Without a SLI bridge, the driver issues a warning. The SLI mode will work, but very limited (see performance analysis).

The first experience of SLI

Hardware

As you know, we were looking forward to the release of SLI. In March, publishing an article on pCI Express bus  , we expected future solutions on several maps. Of course, the subsequent announcement of such a decision from nVidia chained all our attention.

However, after the appearance of the first motherboards with support for SLI, our enthusiasm quickly came to naught. Our test configuration constantly failed, and the GeForce 6800 and 6600 GT PCIe cards either were not recognized at all, or the computer "flew" a few seconds after loading. After many unsuccessful attempts to launch the SLI system, we found the reason: the cards were too "old". Our models relate to the very early samples of nVidia, and, according to the manufacturer, they do not work properly with SLI. However, these cards have not been sold for a long time, and this should hardly be given special attention. The latest 6800 Ultra and GT cards work with SLI technology without any problems. Here, of course, the question arises - can I then purchase a second video card for SLI work from another manufacturer? While we do not know the answer.

We also had considerable problems with SLI motherboards. The ASUS A8N-SLI card completely reset the BIOS every time we restarted the computer - and this problem was not just on our test card. Because of the limitations of the testing time, we could not change the fee for another. As it turned out later, the cause of the failure was a batch of defective BIOS chips. Fortunately, the BIOS chip is in the socket, so we were able to replace it quickly. After that, the A8N-SLI Deluxe earned without any problems.

The MSI K8N Diamond, on the other hand, had memory problems when working in SLI. Our Kingston HyperX memory modules in 2/2/2/6/6 DDR400 mode led to a permanent system crash. The computer was loaded and worked with desktop applications and even with Prime95 in 2/2/2/6 mode, but immediately "crashed" when SLI mode was enabled in most games. When using one card, this problem does not arise. Only after we increased the delays to 2.5 / 3/3/7, the MSI K8N Diamond board worked steadily in the SLI mode. Our test card also had problems with memory bandwidth. Even with delays of 2/2/2/6, the Sandra test produced a memory bandwidth of only 4.9 GB / s, which corresponds to DDR 333! For example, the ASUS A8N-SLI card yields slightly less than 6 GB / s.

Then we had to increase the memory latency for SLI and ASUS work, as in the 2/2/2/6 mode and it crashed. When switching to 2/3/3/6, the board worked stably. As we believe and hope, these problems are related to the test status of motherboards, and they will not appear in retail versions. In recent weeks, ASUS and MSI have arranged a real race for who will be the first to release the SLI work card. As you understand, "hurry up - people make fun of." Problems were to be expected. In addition, most of them occur only in the SLI mode.

After eliminating the described hardware problems, the SLI configuration was immediately recognized by the video card driver. After enabling SLI mode and restarting the computer, everything worked correctly. SLI operation becomes visible only when using the FRAPS frame counting utility in the game. The quality of the image was no different from the usual mode - no lines, flicker or other artifacts, we did not notice. Only by enabling the SLI HUD mode in the driver, which shows the distribution of screen portions for rendering in SLI mode, you can judge the operation of SLI.

After installing the SLI system, the driver 66.93 correctly recognized everything.

By enabling HUD mode, you can see the load distribution between the two cards.

FROM motherboard  nothing much to do is not necessary - except that download latest version  nForce4 drivers.

After several tests, we found a relatively slow performance in two games. After turning on the SLI HUD in the driver, we saw that in these games SLI is not activated. Even forced inclusion of SLI in advanced driver settings did not lead to the desired effect. After talking with the representatives of nVidia, we found out the cause of the problem: SLI really does not work on some games. nVidia uses the so-called SLI profiles for games that are defined in the driver. The driver recognizes the game through application detection technology and includes the desired SLI (split or alternative) mode specified in the profile. If the SLI profile for the game does not exist, then the SLI mode will not be enabled. You can not force SLI mode or create your own profile. However, according to nVidia, the driver already has more than 50 profiles for games, where the SLI mode will be turned on. If the game is completely new, then the owners of SLI, probably will have to wait for the release of a new driver. But even then there is no guarantee that the SLI mode will be included in this or that game.

According to nVidia, there are games that are simply incompatible with SLI. For example, Microsoft Flight Simulator 9 and Novalogic Joint Operations. The reason for the time of publication of the article, we do not know for sure. nVidia only indicates that these games use frame buffer technologies that cause problems with SLI. In general, out of 10 games that we included in our testing, the two were incompatible with SLI.

Theoretically, the PCI Express standard allows you to connect an infinite number of parallel PCI Express lines, but the new desktop chipsets are limited to 20 lines or even a smaller number. If you take into account that the PEG slot (PCI Express for graphics-PCI Express for graphics) already takes 16 lines, then for all other slots there are only four.

nVidia cheated a little with the release chipset nForce 4  . When working with one video card, all 16 lines are available. But when switching to SLI mode, 16 lines are distributed between two slots x16. So each PEG slot works in x8 PCI Express mode.

However, in practice, such a solution has almost no effect on performance, because the throughput of x8 PCIe corresponds to AGP 8x. As the comparative testing of x8 and x16 PCIe modes  , this does not lead to tangible differences in productivity.

Motherboards with SLI support

ASUS supplies the A8N-SLI with a good set of accessories.

The ASUS A8N-SLI Deluxe card is well equipped. ASUS increased the distance between the x16 PCIe slots by placing two x1 PCIe slots between them. A small card determines the operation of one or two graphics cards, depending on which end is inserted. Spring fasteners "EZ Switch" facilitate the process. In SLI mode, you need to connect an additional Molex power plug (EZ Plug). The fact is that the PCI Express specification allows a maximum power of 75 watts per slot x16. According to ASUS, without additional power connection sLI systems, power supplies which are equipped with 20-pin ATX plugs, there may be problems. In the manual, ASUS recommends the use of ATX 2.0 power supplies that have 24-pin plugs - even though using additional connector  power supply. Unlike MSI, ASUS explains that two GeForce 6800 Ultra cards can load a 12-V power supply line up to 14.8 amps. If you are using the Athlon FX-55, then add another 8.6 A. The old 20-pin ATX power plugs (1.0) provide only one 12-volt line. As a result, due to the high continuous load on this line, the power supply can fail . New ATX 2.0 power supplies use a 24-pin connector, where there are two 12 V lines, which allows you to distribute the load between them. Thanks to the ASUS EZ Plug, the power supply can even better distribute the load. ASUS recommends using a 450W or higher power supply for SLI systems with Athlon FX-55 and GeForce 6800 Ultra, since only these components will require at least 281 watts.

The only drawback, we think, is the active cooling of the north bridge. As experience shows, the fan can relatively quickly fail. It would be better if ASUS used only a radiator.

Appearance A8N-SLI (click to enlarge).

This small card translates the motherboard into the mode with one or two slots.

ASUS provides two additional x1 PCI Express slots and three PCI slots.

Extra power for the second video card in SLI mode. If you forget to connect it, then when using the second card the red LED will light up.

At first glance, the MSI K8N Diamond board is very similar to the ASUS model. At the same time, MSI has placed two x16 slots closer to each other. Between them, too, is a small board for setting the operating modes (one or two video cards), but this time it is fixed at an angle. MSI decided not to add additional PCI Express slots. For the second slot x16 additional power is also not provided. In order for the two-card system to work without problems, it is recommended to use a powerful power supply with a 24-pin power plug. According to MSI, a 20-pin ATX plug can also be used if the power supply delivers not less than 18A on the 12 V line. Here, the MSI and ASUS assertions differ somewhat, since the latter indicates that the SLI system requires more.

The fan of the north bridge is located next to the second slot x16, and the video card closes it. However, it has a small thickness, so the map does not interfere.

The appearance of the K8N Diamond motherboard (click to enlarge).

A small card switches the motherboard into a mode with one or two graphics cards.

MSI does not provide additional x1 PCI Express slots, so you'll have to settle for three PCI slots.

MSI recommends a 450 W power supply for SLI systems. When using a 20-pin ATX plug, make sure that the 12 V line is at least 18 A.

The lack of additional power can lead to problems with ATX power supplies, equipped with 20-pin plugs.

Test configuration

We tested the SLI configuration with GeForce 6800 Ultra and GT cards with both ASUS and MSI motherboards. To test the performance of a single video card, we used only the ASUS board. As a processor, we took the Athlon 64 4000+ (it corresponds to the Athlon 64 FX-53) and equipped the system with 1 GB of memory. We used the Antec True Control ATX (1.0) power supply with a 20-pin plug. Note that during testing we did not find any problems. We also tested a 760-watt power supply for the workstation, when we checked whether the stability problems associated with malnutrition were connected.

Due to the stability problems described above, we decided not to run tests for "overclocking".

Test results

Unreal Tournament 2004, special timedemo (level of Fallen City, Assault):

Call of Duty, version 1.4, built-in timedemo timedemo1:

Doom 3, built-in timedemo demo1

Farcy, version 1.3, special timedemo cooler01, the flashlight is on

The Sims2, the selected Goth Family scene (5 seconds with FRAPS)

Flight Simulator 2004, version v9.1, a specially recorded video, the script "Hong Kong At Dusk" (FRAPS):

Battlefield Vietnam, version 1.2, the map "Ho Chi Minh Trail", Gameplay Measurement (FRAPS)

Half-Life 2, special timedemo THG2

Half-Life 2, special timedemo THG5

Half-Life 2, special timedemo THG8

Performance Analysis

Our first tests immediately showed that the SLI mode requires a very powerful CPU. With the fastest GeForce 6800 GT and Ultra cards in SLI mode, even the fastest processor does not have time to provide them with data. All the power of SLI is noticeable only at high resolutions of 1280x1024 or, better, 1600x1200 with the inclusion of FSAA and anisotropic filtering - that is, in those scenarios that most load modern graphics cards. With lower resolution and disabled FSAA and AF, the SLI mode provides little benefit. By the way, on some games the transition to SLI gave even some deceleration (UT 2004), which, probably, is connected with additional computational costs for load distribution, which SLI entrusts to the CPU. At the same time, we found a performance drop in SLI mode even on Flight Simulator 2004, compared to a single card, despite the fact that FS2004 does not support SLI mode at all. Or, in other words, if only one card works in the SLI system, the performance will decrease compared to the computer where only one card is installed. Not much, but tangible.

Below we gave an example of the game Unreal Tournament 2004. We used the GeForce 6800 GT in a resolution of 1024x768 without FSAA and AF. Both in SLI mode and in normal mode, the CPU could not keep up with the graphics card and load it with enough data, being a bottleneck. The more powerful the processor, the higher the performance:

• sLI mode is enabled (2 cards): 157.2 FPS;
• sLI mode is off (2 cards): 163.2 FPS;
• one card (1 card): 163.4 FPS.

If this phenomenon can be explained in UT2004 and other games (probably the SLI load distribution lays additional calculations on the processor), then we do not understand why this situation occurs in games that do not support SLI, where even with SLI switching only one card works (Flight Simulator 2004). By the way, in games OpenGL, such as Call of Duty, this problem is not so tangible.

If the game actively uses shaders (for example, Doom 3 and FarCry), then the performance gain of SLI compensates for any shortcomings at high resolutions and enabled quality settings.

The type of game also has a considerable effect on the effectiveness of SLI. Games with old 3D engines like Call of Duty benefit from SLI only at high resolutions and enabled quality settings. But performance here is already very high without SLI, so there will be no problems. At the same time, modern games that actively use shaders (for example, Doom 3 and FarCry) demonstrate the advantage of SLI even at small resolutions.

To dispel all doubts about the observed phenomenon of performance degradation at low resolutions in SLI, we analyzed the performance of one card in x8 PCIe and x16 PCI modes. The results were completely identical.

Finally, our last measurement concerns UT2004 without a connected bridge SLI at 1600x1200 resolution 4xAA / 8xAF:

• with a bridge SLI (2 cards): 153.3 FPS;
• without bridge SLI (2 cards): 133.0 FPS;
• one card (1 card): 101.1 FPS.

In addition to the standard work of SLI on motherboards, you can implement two more scenarios. Instead of having two video cards working together, you can use them to connect up to four monitors to a computer. And this mode of operation is not limited only to nVidia cards - we have not experienced any problems when installing X800 or X700. After boot Windows  I recognized the second card and installed the driver.

At the same time, the latest drivers ATi CCC (Catalyst v4.11) have some problems with the recognition of this mode of operation. The Display Manager Wizard recognizes the outputs of only the first card, although the Display Manager shows three monitors. In either case, you will not be able to change the resolution type parameters, etc. for all monitors. CCC allows you to set these parameters only for the first X800 card. When you try to click on a display connected to another card, the CCC immediately goes to the first display. On the other hand, adjusting the settings in the Windows Display Manager runs without any problems.

Microsoft Flight Simulator 9 launched without any problems on three displays in the mode of two and three displays on X800 and X700 cards. At the same time, the "3D-span" mode on two ATi cards is not possible yet. We will try to find out the reason for ATi and let you know later.

Now let's move on to nVidia. We decided to install the GeForce PCX 5750 in the second slot, and the first one - the GeForce 6800 Ultra. The second card was again recognized by Windows without any problems. In the driver menu of nVidia, both cards appeared, so that the settings can be carried out separately. However, the "span" mode for combining three monitors into one big screen (like the Matrox Surround Gaming function) with nVidia cards is impossible, even if the second card installs the GeForce 6800 Ultra. The "span" mode is limited to only one card - not too good! For some reason, when using two cards in the nView settings, the nView Display Wizard was unavailable.

The result will be as follows. Support for three or four displays through two video cards on SLI motherboards still requires the development of drivers. If the "span" mode was not limited to one card and two displays, then we would get a good configuration for gaming (surround gaming). In the end, Matrox, which developed Surround Gaming, all three monitors work from one card.

Finally, we could not deny ourselves the pleasure of conducting one final test. Even at the time of Voodoo2, users could run 3D games through a standard graphics card or a separate Voodoo2 card. So why not try to install Radeon X800 XT PE together with GeForce 6800 Ultra and do not connect both cards to a monitor equipped with two inputs? So we did.

Installation of ATi Catalyst v4.11 driver together with nVidia Detonator v66.93 did not cause any problems. After the restart, the ATi driver failed because it could not activate the second display. After we corrected the situation in windows menu  Display, we have access to the ATi driver options.

ATi and nVidia in harmony - at least on our computer.

Now the ATi and nVidia icons appear on the taskbar.

On the first card GeForce 6800 games were launched without problems. After we switched the main display to the ATi X800, we got a D3D error when starting the game. Restarting the computer did not help.

Changing the cards, we installed the X800 in the upper slot - the system did not work at all. After determining the graphics cards and rebooting geForce driver  6800 could not boot correctly, although the card was still present in Device Manager.

But we do not give up so easily! So we went back to the configuration when the GeForce 6800 Ultra occupied the first slot, and the X800 XT was the second. Again, we defined the X800 as the main monitor. In addition, we turned off the GeForce 6800 display by disabling the "Extend my Windows Desktop on this Monitor" windows Wallpapers  on this monitor). Restarted - and now all 3D-games have earned and on the X800!

Below we have resulted step-by-step instructions. First, only the GeForce 6800 Ultra is activated. NVidia drivers  and ATi are installed as described above.

3D Mark 2003 runs on the GeForce 6800 Ultra.

In the Windows Display Manager, the Radeon X800 XT card is disabled (display 2).

After clicking on the second display, select the option "Extend my desktop on this monitor" and then the "Use this device as the primary monitor" option and click "Apply". Now switch your monitor to the second VGA input.

Now select the first display with the mouse and turn it off by unchecking the option "Extend my desktop on this monitor".

After you click "Apply", the GeForce 6800 card will be turned off.

Running a 3D application produces an error message - time to reboot!

When the PC is booted, the screen will initially be black, as all boot messages are output through the first card (GF 6800), and our monitor's input is connected to the X800. After loading Windows, a picture appears, and the GeForce 6800 card turns off.

After the reboot: run 3D Mark 2005 - all is well!

Switching back to the GeForce 6800 is exactly the same. But for some reason the GF 6800 first starts only with a color depth of 4 bits! Do not worry. After rebooting the computer, you can set the correct resolution and color depth.

Of course, this mode can not be called convenient, since it requires a computer restart, but it still works. You can choose between ATi and nVidia cards on one computer!

Conclusion

This could be expected: a computer with support for SLI, equipped with two cards GeForce 6800 Ultra or GT wins the performance of all the others! The performance reserves of the SLI system are simply superb. Even with the Athlon 64 4000+ processor, performance almost always rested on the CPU - it just did not have time to calculate and issue information to the cards. Only at a resolution of 1600x1200 pixels with the inclusion of 4x FSAA and 8x anisotropic filtering, SLI cards were able to get sufficient load. The form of the game, too, in no small measure affects the performance gain provided by SLI. If the game is heavily using shaders (for example, Doom 3 and FarCry), the advantage of SLI will be noticeable even at low resolutions. At the same time, on relatively old games such as UT 2004 and Call of Duty, the gain is smaller. By the way, even Half-Life2 gets a relatively small increase from SLI. It should be noted that some games in SLI mode will not be able to start at all.

The performance of the SLI system on two GeForce 6600 GT cards will be evaluated only when new test cards arrive at our laboratory. One thing is clear right now: the SLI system can not be assembled easily.

When buying an SLI system, be aware that this mode is not supported by all games. If the driver does not find a suitable SLI profile for the game, the game will work with one card even when SLI is turned on - and the performance in this case may even decrease compared to the system in which only one card is installed. This is largely influenced by the age of the game and the level of 3D technologies in it. Another financial problem is connected with the fact that retail prices for GeForce 6800 PCIe cards and SLI-compatible motherboards are still unknown. So far, we've heard about the price increase by about $ 50 compared to the standard motherboards for nForce4 Ultra.

Among the tested SLI-compatible motherboards for nForce4, our choice fell on ASUS A8N-SLI Deluxe. And not only because of better performance. Although MSI will no doubt solve the memory bandwidth issue in the final version of the motherboard, the ASUS model provides two additional x1 PCI Express slots that MSI does not have. Another factor is additional food  for the second video card on the ASUS motherboard - it looks like the manufacturer came here more thoughtfully.

We do not agree that SLI support today is only possible on games released together with nVidia. Similar to "overclocking", it would be nice to get an option in the drivers that forces SLI work, even if it leads to potential errors and crashes. After all, SLI technology is aimed at enthusiasts! Anyone who agrees to invest $ 1000 in the graphics subsystem of their computer can accept the risk that the game or computer will sometimes "crash" in SLI mode. In our opinion, it's not too much fun waiting for the next version of the driver or using a "leak" driver for a new game. It is unlikely that this should be done with the target audience for which SLI technology is intended.

Another use of SLI motherboards can be considered the use of configurations with more than two monitors. And some fanatics can install ATi and nVidia cards simultaneously on their computer.

The theoretical performance of modern video cards reaches one trillion floating point operations per second. This is ten times more than the fastest quad-core processors ... Alas, but computer games on theoretical  speed spit. Gluttonous games like Crysis  even the most outstanding video adapters of our time are being pardoned. And here technology comes to the rescue NVIDIA SLI  and ATI CrossFire, allowing you to use two or more video cards at once.

NVIDIA SLI

Legendary Voodoo 2. It was the first time it tested SLI technology.

Various variations of connecting bridges for SLI.

The abbreviation SLI appeared about 10 years ago. That's when the company 3dfxunveiled a technology called Scan Line Interleaving, which in translation meant "interlaced scanning of frames". The first device with support for SLI was the legendary 3D accelerator Voodoo 2. It was a separate board with a PCI interface and two connectors: the first was connected to the monitor, and to the second - a special cable that connects Voodoo 2 to the video card already in the computer. When working in two-dimensional applications, the accelerator was idle and simply transmitted the signal from the video card to the monitor. But when you start three-dimensional games Voodoo 2 took on all the processing graphics. To assemble the SLI-system, it was necessary to install a second accelerator and connect it to the first. As a result, we got a heap of cards, which occupies three PCI slots, because neither AGP, nor PCIe x16 was there.

The principle of operation of such SLI is extremely simple: two accelerators computed the lines of the image one by one, that is, one card calculated even lines, the other one - odd. Needless to say, the technology for that time was revolutionary, and Voodoo 2 itself was a very successful accelerator. Unfortunately, in a couple of years the 3dfx business became completely bad, and the company, together with all its developments, bought NVIDIA. For SLI came a long period of calm.

The return of SLI took place in 2004, largely due to the appearance of the PCIe x16 interface. It provided the necessary bandwidth, and the system could have two x16 PCIe slots. The decoding of the abbreviation SLI has changed: henceforth it meant Scalable Link Interface- "scalable connection interface".

A typical SLI configuration.

The principle of the algorithm is Split Frame Rendering.

SLI algorithms have also changed. Instead of interlacing frames NVIDIA proposed to use two new methods to choose from. The first is called Split Frame Rendering  (SFR): the image is divided into two parts, each of which is processed by a separate video card. The proportions of the parts may vary depending on the degree of loading on each of the boards. Let's say that there are a lot of complex objects at the bottom of the frame, and only the sky texture at the top. Then the video adapter that processes the top of the scene will take over most of the frame. Unfortunately, when working in SFR mode, both boards are forced to process the whole frame geometry, which does not have the most beneficial effect on performance.

The second algorithm is called Alternate Frame Rendering  (AFR). When it is turned on, video cards begin to process frames one at a time: one gets even, the other gets odd. In AFR mode, each card calculates the geometry of its frame, and in theory, the performance here should be higher than in the case of SFR. However, in dynamic scenes saturated with sharp changes in frames, when using AFR there are unpleasant jerks. The problem is the unevenness of the load: the video card, which quickly coped with its scene, is forced to stand idle while the second board copes with its shot. Because of this, the SFR mode even with a smaller average number of frames per second often provides a more comfortable level of play. Just due to smoothness.

For building modern system  NVIDIA SLI requires the following components.

Two identical video cards  from NVIDIA family GeForce 7000  or GeForce 8000. There are older graphics adapters with SLI support, but today they are not relevant. Frankly, office models, like GeForce 7200 GSalso we do not take into account. Technology in its current form allows you to use two video cards from different manufacturers and with different core or memory frequencies (they automatically equalize). The BIOS versions may also vary.

Connecting bridge. Usually it is included in the package of the motherboard. If you suddenly want to organize an SLI on the basis of two GeForce 7100 GS  or GeForce 7300 GT / GS / LE, the connecting bridge will not be needed - the video cards will be combined at the program level.

Motherboard  on one of the chipsets NVIDIA nForcewith two PCIe x16 slots. The boards for SLI differ from each other in the modes of operation of graphic connectors. There are schemes "x8 + x8" and "x16 + x16": in the first case, to each of the PCIe x16 slots, there are 8 PCIe lines, in the second - 16. To date, most graphics tandems are equipped with a motherboard supporting SLI in the x8 mode + x8 ". However, when using flagship graphics cards, it is better to give preference to a model with full PCIe x16 connectors. So you will provide yourself with a small additive in speed.

ATI CrossFire

Video card RAGE FURY MAXX  - ATI's first experiment on combining two graphics chips.

Technology CrossFire  was presented to the world in September 2005. However, this is not the first time when a pair of graphics chips were used in one system ATI. At the end of the last century, a video card appeared RAGE FURY MAXX, which contained two chips at once RAGE 128 PRO. It provided high performance in games, but due to a number of hardware and software errors it did not become popular.

The SuperTiling mode is exclusive to AMD.

Modern graphic tandems ATI support three modes of operation: the already mentioned Alternate Frame Rendering, Scissors  ("Scissors") - an exact copy of the Split Frame Rendering mode from NVIDIA, and SuperTiling, which is really interesting. When using the last algorithm, the frame is divided into a set of squares with dimensions of 32 by 32 pixels. This can be most clearly illustrated by the example of a chessboard: white cards are processed by one video card, and black ones by another. The load between the boards is distributed evenly, but, as in the case of SFR / Scissors, each video adapter must calculate the geometry of the entire frame as a whole. When you start the game, the driver Catalyst  automatically selects one of the three modes of operation, which, in his opinion, is best suited for this application.

In the early stages of CrossFire development, it was impossible to assemble a bundle of two identical boards. One conventional video card was required, and the other one was from the same series, but with an additional chip Compositing Engine. Models Radeon, intended for mode CrossFire, were called master cards, and to their names was added a prefix CF. To connect the two video cards to each other, a special external Y-shaped cable was used, consisting of two DVI-I connectors ("mother" and "dad") and one DMS-59. Need I say that the composition of a pair of boards and a cable dangling behind the system unit, was far from perfect?

The principle of Alternate Frame Rendering is Radeon.

Time passed, and technology developed rapidly. ATI offered a software version of CrossFire, which did not require the use of connecting cables - video cards exchanged information via PCIe x16 connectors. For the first time the software connection was tested on younger Radeon models, and only then on more powerful video cards. Modern ATI cards (or rather, AMD), like NVIDIA cards, are connected using special bridges.

CrossFire technology is very democratic in terms of choice of video cards: any two models with similar architecture are suitable. For example, you can combine video cards Radeon HD 2600 Pro  and Radeon HD 2600 XT. But there is one point: the characteristics of a more powerful video adapter will be reduced to the values ​​of a weaker one. In the case of our example, we get the CrossFire-system as if on two Radeon HD 2600 Pro.

Chipsets compatible with CrossFire are released not only by AMD, but also by Intel. However, of all the Intel chipsets, only one X38 can boast of official support for this technology in the "x16 + x16" mode. On the other cards CrossFire works according to the "x16 + x4" scheme. In general, the difference between modes is minimal. If you do not plan to set high-speed records, then there is no special need for two full PCIe x16. On AMD chipsets, graphics connectors work in symmetrical modes "x8 + x8" or "x16 + x16". The only exception is AMD 570X.

Invasion of hybrids

AMD and NVIDIA are actively promoting the idea of ​​combining a conventional graphics card and the integrated graphics core of the motherboard. Appropriate technologies are called Hybrid CrossFire and Hybrid SLI.

The built-in graphics never differed with outstanding work speeds, so do not expect a serious increase in performance from the use of "hybrids". And then only those owners of inexpensive video adapters will be able to feel this increase. By the way, younger models of video cards should be the first to provide technology support.

The main advantage of using "hybrids" is associated with energy savings. When the computer is working with 2D graphics, the embedded kernel is running everything. But in the games to it the main video card will immediately join.

According to forecasts, official announcements of Hybrid SLI and Hybrid CrossFire should be held this spring.

When the tandem is not enough

A bunch of 3-Way SLI is the choice for the most desperate enthusiasts.

A bunch of two video cards can significantly improve system performance. However, there are cases when such speed is not enough. And at the end of last year NVIDIA introduced new version  SLI, which allows you to combine three video cards at once. The technology is called 3-way SLI.

At the moment, three versions of SLI support only two models of video cards: GeForce 8800 GTX  and GeForce 8800 Ultra. The reason for this discrimination is that only these video adapters have two slots for connecting SLI bridges. The bridge itself is non-standard: there are not two, but six connectors. By the way, theoretically, video cards can be connected and using three conventional bridges: two hard bridges and one flexible.

Modern motherboard with four PCIe x16 slots and support crossFire technology  X.

To build a 3-way SLI system, you will need a motherboard based on a set of NVIDIA system logic and equipped with three x16 PCIe slots. It's about models based on chipsets nForce 680i SLIand nForce 780i SLI. It is also strongly recommended that the processor is more powerful, or even better - the most powerful. At the moment it can be considered as such Intel Core 2 Extreme QX9770. It should be noted that of all SLI-compatible motherboards this processor is only friendly with the models on the nForce 780i SLI chipset.

As for the performance gain, then everything depends on the specific application. As practice shows, in the presence of a fast processor, the advantage from using three video cards in comparison with two can reach 30-35%. However, all its advantages the technology reveals only at very high resolutions (1920x1200 and higher) with high filtering and anti-aliasing settings. It is understandable: it is unlikely that the owner of a system with 3-way SLI will run games in 1280x1024 resolution with standard quality options.

The competitor in the face of AMD is not slumbering. The company has been developing for a long time CrossFire X  - Your answer to the 3-way SLI. AMD plans to release a driver, which will allow to combine in one system not only three, but also four video cards. To connect the video adapters will use the same flexible bridges, as in the case of the classic CrossFire.

Motherboards with four graphics connectors are not uncommon - all thanks to the chipset AMD 790FX. The boards based on it provide two full-fledged PCIe x16 interfaces for conventional CrossFire. When you add a third or fourth video card, the connectors automatically switch to x8 mode. 790FX supports only AMD processors, but Intel fans should not despair. A number of companies (for example, MSI or ASUS) sell motherboards with four graphic connectors, but based on the set of system logic Intel X38. Far from the fact that the driver CrossFire X will provide support for technology on these boards, but there are no obstacles to this.

If you compare SLI and CrossFire technology to the forehead, then the NVIDIA creation looks more powerful. But the times when CrossFire was openly weaker than the competitor, have already become the lot of the past. However, the problems associated with the use of a graphic tandem, NVIDIA is still smaller.

Is it advisable to build a system with two video cards? First, we must understand that SLI and CrossFire are not a panacea. If the PC is poorly balanced, and in the role of "bottleneck" is the processor or rAM, then the graphical tandem will have little effect on performance. Secondly, two video cards consume a lot of energy and emit a lot of heat. Therefore, before assembling it is necessary to acquire a spacious casing and a powerful high-quality power supply. Thirdly, both technologies strongly depend on the optimization of drivers and games. It is difficult to foresee how much faster the performance in an application from using a second video card. Sometimes there may be no growth at all.

Does it make sense to collect a tandem from two boards of the middle price segment? Everything depends on the specific situation, but in most cases, buying one more powerful video card looks more reasonable. No expensive motherboard is required, and there will be less maintenance problems.

New quality standards

The scheme of work of algorithm Super AA.

SLI and CrossFire can be used not only to improve system performance, but also to improve image quality. These are the anti-aliasing modes SLI AA  (for GeForce video cards) and Super AA  (for Radeon).

When SLI AA is enabled, each of the video cards completely processes the same frame, but with different patterns of full-screen anti-aliasing. After that, the frames are superimposed on each other and the colors of the corresponding pixels are averaged. Thus, the quality of anti-aliasing is doubled. The available SLI AA modes are x8, x16 and x32.

The Super AA method works on the same principle as the development of NVIDIA. The only difference is in the available anti-aliasing modes: 8x, 10x, 12x and 14x. Modes 8x and 12x are respectively "doubled" versions of 4-fold and 6-fold multisampling, in modes 10x and 14x, multisampling is added 2-fold supersampling.

Hello, a question!  I bought two geForce video cards  GTX 1070 for 38 thousand each and installed them in your computer in a bunch of SLI, but the results intests in Futuremark 3DMark show that performance (compared to a single video card) increased by only 10-15%, and I was waiting for at least 50%. Also in modern games, two vidyuhi did not raise me FPS, and in some (in particularFAR CRY PRIMAL) even downgraded. It turns out that it would be better for me for this money I bought not two but one video cardGeForce GTX 1080 or even GeForce GTX 1080 Ti. And so I threw money away. Do not repeat my mistake. And yet, few people know that the NVIDIA graphics cards of the tenth series can not all work in bridge mode (SLI), for example, GeForce GTX 1050 and GTX 1060 can not, alsoThe GTX 1070 can not be bundled with the GTX 1080 . Tell us about it on your website.

Hello! Almost all users who like to chop into different toys, for sure thought about or heard about the fact that you can put two or more video cards in the system to combine their power. Actually, the technology of combining two or more graphics processors for 3D image processing 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 I will tell about it today.

• And most importantly, I'll tell you why it's unprofitable for video card manufacturers to use SLI or CrossFireX technologies to increase the performance of the computer's graphic system by 100%.

So, let's start with the green ones (Nvidia). In order to put yourself in the SLI system bundle you will need 2+ video cards of the same series and one model. Unlike the reds (AMD) (which we'll talk about a bit later), graphics processors are more finicky in this regard. If the older rulers of cards allowed to unite absolutely any models in the bridge (the main thing that they were the same), then in the last tenth line everything changed. You can build a bridge only from the GTX 1070, 1080 and 1080Ti. With what it is connected personally for me remains a mystery, but, unfortunately, now only these models can be combined. I can not give any information about the Titans.

(Two GTX 1080 Ti video cards connected by a SLI bridge)

As for the Reds, they have both advantages over green, and drawbacks. The main advantage is that it is possible to combine absolutely any models, the main condition is that the combined video cards be built on the same architecture. For example, AMD is able to put AMD in a bunch of RX 460 and RX 470. But put the GTX 1070 and GTX 1080 in a bunch will not work. Well, the main disadvantage of CrossFireX is the performance gain. The increase in power when using direct competition cards for reds is much lower than for green cards. And the optimization in most games supporting the bundles of video cards 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 970s, one from MSI, and the other from Palit, this will not affect the result in any way. This rule applies to both video cards from Nvidia and AMD cards.

To build a system on sLI-based  and CrossfireX you will need:

1. A motherboard with two or more PCI-express x16 connectors that supports this technology. Not all mothers who have two or more connectors for video cards support a bunch of video cards! On the motherboard itself there is always a corresponding marking on the manufacturer's website about it written, as well as always indicated in the attached instructions. Remember that if you do not need a mother who supports SLI and CrossFireX, then choose the appropriate card, since you always overpay money for the fact that the mother is equipped with video card communication support.

2. Powerful power supply. Two video cards = large power consumption. A block of 550 watts is recommended.

3. The video cards themselves supporting the technology.

4. Bridge connecting video cards. As far as I know, AMD allows you to combine maps without using this bridge, that is, using software. However, in this case, the performance losses will be about 15-20%, rather than if you used a bridge.

In my opinion, it is not worth building a system based on these technologies. It's not worth it, because it's better to buy one more powerful video card, rather than two, but weaker. 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, in green it is certainly better than the red ones, but still bad. The increase in performance, as you might think, will not be 100% of the use of the 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 expediency of such a purchase remains open in terms of price / performance. Putting yourself such a system makes sense only if the power of the top-end video card at the moment is not enough for you. And this happens only in very narrowly 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 handles this task calmly. Or if you want to play in high resolution - 4 or 8k.

Also do not forget about video memory. In case you combine two video cards with different amount of memory, only the memory that is smaller in size is used. For example, you put the RX 480 with 4gb and RX48 with 8 gb. As you might think, you will have 12 gigabytes of video memory. Unfortunately, it is not. Only 4 gigs will be available. If you have two identical video cards, but working on different frequencies, then in that case they will both work on the lower frequency. That is, for example, one works at 1544Hz, the other at 1622Hz, both will work at 1544Hz. In the future, with the full transition to DirectX 12, we are promised full optimization and full utilization of all the resources of the combined video cards. That is, there will be a 100% power increase and a complete summation of the available video memory. But this is all a promise, in fact we have what we have. Of course, there are some interesting game projects where we can get 70% and 80% of the productivity gains, but unfortunately they are very few and they are rather an exception to the rules. As I like to repeat, it's up to you to decide, ultimately, only to you, and I for a long time already decided that at the moment SLI and CrossFireX are extremely impractical!

Why will video card manufacturers never bring SLI and CrossFireX technology to mind and why the second graphics 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 of its power you were not enough. You went to the store or to the secondary market and bought an inexpensive second such a video card, as a result added 100% performance to the graphics system of your computer. But this will never happen! To the manufacturer it is unprofitable, but it is advantageous that you always buy a new product and at an expensive price. That's the whole secret. That's it, see you soon!

AMD Radeon came the turn and the company Nvidia. Its GeForce graphics processors are no less popular among players than the products of the competitor. Both companies keep pace in the market, offering customers solutions similar in terms of productivity and price. Therefore, it would be unfair to devote the material to building a CrossFire configuration, but bypassing the similar capabilities of Nvidia products.

A bit of history

The beginning of the era of SLI can be considered 1998. Then the company 3dfx for the first time managed to realize the possibility of combining several video cards to solve one problem. However, the development of the AGP interface slowed development in this direction, since all motherboards of that time were equipped with only one slot for a video card.

SLI from 3DFX - "grandfather" of modern technology

After in 2001, 3dfx were bought by Nvidia, all developments in this direction were waiting for their time, which came only in 2004. It was then, in the 6000 series GeForce (the first video cards designed specifically for the newest PCI-Express interface at the time), the available designs were improved and introduced into mass-consumption products.

SLI of two GeForce 6600GT

First, you could combine two GeForce 6600 or 6800 video cards, with the output of the 7000 series (in which the first full-fledged dual-processor board from Nvidia, 7900GX2 was presented), it became possible to build a four-processor configuration (of 2 cards), and later a combination of 3 or 4 separate GP.

How to combine video cards in SLI: requirements

As for CrossFire, it's not enough to buy two video cards Nvidiato configure them in the SLI. There are a number of computer requirements that must be followed to ensure the proper functioning of the ligament.

Which video cards can be combined into SLI

Connecting two SLI video cards-It is possible only if there is an interface on the board for this bridge. Software can combine them, too, you can try, but without "dancing with a tambourine" in this case can not do. And it does not make sense to build a tandem of two GT610 or GT720. One card, the speed of which will be higher than that of a similar bundle, 2 or 3 times, will be cheaper than a set of a pair of office cards and a compatible motherboard. That is, the lack of graphic accelerators on the younger representatives of the SLI-interface is caused not by the producer's greed. No one puts the bridges, because this will make the card more expensive, but there will be no meaning from them. In this way,connection of two SL video cardsI is possible for models of medium and top class. These include GPUs, the second digit of which is 5 or higher (GTX55 0Ti, GTX96    , GTX6 7 0, GTX7 8 0, etc.).

The GeForce GT 720 does not have a bridge for SLI

Before , how to connect SLI two video cards, it is worth making sure that they are built on one version of the graphics processor. For example, GeForce GTX650 and GTX650Ti, despite the similarity of names, operate on the basis of completely different GPs and therefore can not work in tandem.

Is there any practical benefit from SLI?

Before, how to combine video cards in SLI,  it is advisable to familiarize yourself with the experience of using such configurations by other gamers and study the specifications of their cards, as well as the characteristics of more productive solutions in the line. Often, neither in terms of savings, nor in performance, win two-card configuration does not. For example, two GTX950s in SLI show results comparable to one GTX970. The difference in price (about 200 and 400 dollars, respectively) of the cards themselves is justified, but if you consider the additional costs for a powerful PSU, a dual-slot motherboard, a quality and well-ventilated case - it looks doubtful.

A completely different situation, if  - part of the procedure for upgrading an existing PC purchased a couple of years ago. The cards of the GTX650Ti or GTX750 level can still be found on sale at a reasonable price (the difference with the new models is roughly equivalent to the speed difference), and the technical progress for 3 years did not present anything revolutionary for the graphics cards (except that the HBM memory presented by AMD, but Nvidia is until it touches). Therefore, the addition of another graphics processor is a very rational step for such players.

SLI: connection of video cards

If the computer meets the requirements for creating an SLI configuration, a suitable second video card is purchased - you can proceed to the assembly. After turning off the PC, remove the cover of the system unit, install the second card in the corresponding slot, connect an additional power cable (if required) to it and connect the two cards with the bridge that comes with it. Hardwareconnection of two video cards in SLI  this is completed and you can proceed to the software configuration.

Power Cables Connected to SLI Link

Connecting two SLI video cards in Windows

In order for the bundle of two GPs to function properly, you need to install it on a PC Windows versions  Vista or newer (7, 8, 8.1 or 10). It is also recommended to download the latest version of the driver for the video card from the Nvidia website. After that you can proceed to setup.

After applying the settings, the bundle is ready for use. Perhaps, in order to correctly configure SLI operation in some games, you will have to set them special parameters in the submenu "Program settings". But, as a rule, most modern software does not need it.