nVidia SLI Technology - Introduction and 6800 Ultra Performance

We finally get our chance to setup an nVidia SLI system with two GeForce 6800 Ultra graphics cards and see just what type of performance we can expect from this expensive yet impressive setup which deserves respect. Since this is our first SLI article we look into what exactly SLI is, what it stands for, how it works and everything else we think is important and then get straight into the benchmarking to see what we can come up with.
| Jan 26, 2005 at 11:00 pm CST
Manufacturer: none

SLI - Introduction

IntroductionS-L-I...the three letters on the tip of every computer enthusiasts tongue at the moment. Love or Hate PCI Express, it is here to stay and with it we are seeing leaps and bounds in technology with the biggest deal so far being SLI or Scalable Link Interface. We will be today looking at two GeForce 6800 Ultra graphics cards from nVidia which take advantage of the highly anticipated SLI configuration. We will be running all our normal synthetic and Real World game tests but we will also be doing something a little different with our tests results today. While everyone is getting excited about SLI in gaming we go further and see how it impacts our overall system performance at all - is memory bandwidth not as good or is the processor not scoring as well in PCMark. We will be looking at this as well as just what kind of difference two graphics cards gives us...the same kind of performance as a twin turbo vehicle or a let down?We won't be looking at the graphics cards but simply just having a quick look at what exactly SLI is, what it stands for, how it works and everything else we think is important and get straight into the benchmarking to see what an extra $400 gives us and the upgrade to the nForce 4 SLI chipset.The heat is turned up Down Under in our hot Aussie summer and even hotter in our testing labs - let's get down to business and see what SLI can really offer us with two nVidia GeForce 6800 Ultra's.

SLI - What is SLI? AFR and SFR

What is SLI?SLI, AFR, SFR - So many acronyms, all with different meanings. While just about everyone who shows a slight interest in computers knows about SLI, their knowledge on the subject doesn't go much further then the fact that they know you can run two graphics cards at the same time giving almost twice as much performance. While that is the bulk of it, there is more then just inserting two cards into your motherboard, hitting enable, and getting the most out of your games.For starters there are two drawing modes of SLI when it comes to rendering the picture that is being outputted to your monitor. AFR and SFR are the two particular modes we are talking about and we will look at these in more details now.- AFRAlternate Frame Rendering or AFR is the first mode that we will be looking at. What seems to be the most common mode used, the idea behind AFR is that the two GPUs take one frame each. We would see our slot 1 graphics card taking our uneven frames like 1 - 3 - 5 - 7 and etc while the graphics card in slot 2 takes 2 - 4 - 6 - 8. In turn this means that both graphics cards are sharing the work load to what most people would think the most efficient way possible.
Photo courtesy of The Tech Report
While AFR does seem to be the most effective way there are issues with particular games which can cause blurring. This is where the other form of rendering comes into play.- SFRSplit-Frame Rendering or SFR is the other mode available and works by splitting up the frame and let's each graphics card evenly share the work load of each frame. While you may instantly think that the frame is split evenly in half you are assuming wrong as it works by evenly spreading the work load on the complete frame - for example, if you have a picture that had little detail in the bottom half but a lot in the top second half, you would find that the majority of graphics processing power from both graphics cards would be working on the top half of the screen while one is also rendering the bottom of the screen that doesn't require as much processing power to render the particular scene.
Photo courtesy of The Tech Report
Right now in current nVidia SLI drivers you have no way of choosing which form of SLI drawing method you wish to use and this is a negative thing as each game performs better in different SLI modes - given nVidia do test games in-house to work out which SLI drawing method works best for each game, it would be nicer to have the option of choosing a method for yourself. nVidia do plan on allowing end-users to be able to adjust game driver profiles for which SLI mode you wish to use but there is no word on when this feature will arrive.A website called 3DChipset does have a free tool available for download by author Andrew Poison which allows you to create new profiles for your games which do or do not support SLI where you can choose which type of SLI drawing method you wish. However, by the time most users have SLI systems, we'd hope nVidia has addressed this issue in upcoming drivers themselves.

SLI - What parts do I need?

What parts do I need?The most obvious thing that you are going to need is two PCI Express graphics card which are of the same make and model - SLI is not supported on AGP graphics cards. The lowest end SLI capable card is the GeForce 6600GT which has quickly become known for its great bang for buck. From there you move into the 6800 series which consists of the GeForce 6800/6800GT and the biggest bad boys around the GeForce 6800 Ultra's which we have here today. Keep in mind later in the year ATI is expected to deliver an answer to nVidia's SLI with AMR (ATI Multi Rendering) but details on this technology are scarce at the moment.
The most common SLI capable motherboard floating around at the moment is the ASUS A8N-SLI which while it does have a few little issues has quickly become an excellent fixture to any enthusiast's computers. With good availability on the motherboard and its price, it really is a great motherboard and has really proved itself to us here at TweakTown considering the amount of stress we have put it under over the past few weeks trialing out SLI for all it's worth. Other SLI boards are starting to become available from companies such as MSI and DFI but ASUS is clearly at the forefront with an SLI solution out way in front of everyone else.nVidia recommend a quality power supply which is capable of delivering at least 500 watts of power. We have been using an Antec 450 watt power supply though for the last few weeks without any issues. If you are looking at setting up an SLI system, don't be stingy when it comes to buying the power supply. With two graphics cards, come great heat - so case cooling is also essential part of the setup, especially if you intend on overclocking the cards.While these components are extremely important the biggest thing most people need to enter the SLI market is MONEY. There is no denying that jumping on the SLI bandwagon is expensive - according to our price comparison website for a base SLI system at the time of publishing you'll be looking at around $400 US for the two GeForce 6600GT's, around $250 US for the ASUS A8N-SLI motherboard and extra for all the other parts not forgetting the beefy high quality power supply. This adds up to $650 US just for the baseline SLI parts and a lot more for the 6800 Ultra version of the setup.

SLI - Supported Games and Setting up an SLI system

What about game support?While some people may have read articles going around the Internet about SLI not supporting all games, all we can say to that is, "What do you expect?" In nVidia's defense, it's a new and exciting technology which needs time to mature from its current state (which is not too bad at the moment) but as with anything in life, progression is made over time.If we were to write an article every time new tech is released and current generation software is not able to make full use of it, we would see countless articles such as nVidia Shader Model 3.0 Short Changing Gamers? since SM3.0 is still something that a lot of games don't make use of or maybe Intel Hyper Threading Short Changing Gamers? as we have another technology that is great in a lot of programs but not all or AMD 64-bit Processors Short Changing Gamers? because we all know that there are so many games that are able to make use of the 64-bit architecture (that was sarcasm).Shader Model 3.0, Hyper Threading and 64-bit computing are all excellent technology advancements and like anything new we cannot expect the whole world taking advantage of these new features from the beginning. Intel, AMD, ATI and nVidia all release technology that won't make use of current generation software but we know that one day in the not too distant future we will see applications and games make use of these new technologies - things cannot happen over night but they will eventually. With new and fast advancements in technology, some flexibility is required.Here is the current games list that makes use of SLI from the nVidia nZone website: Aquamark3HaloBattlefield 1942 Desert Combat ModPainkillerBattlefield VietnamSims 2City of HeroesStar Wars: Knights of the Old RepublicCode Creatures ProTomb Raider: Angel of DarknessColin McRae Rally 4 DemoTron 2.0Command & Conquer GeneralsUnreal Engine 3Doom3Warhammer Dawn of WarFar Cry3DMark 2003 GoldGround Control 23DMark 2005 GoldHalf Life 2This list of officially supported SLI games from nVidia is only going to get bigger as nVidia continues to work with gaming companies and helps them either implement SLI support into their games or work with them to increase SLI performance in their titles.Editor's Note - While we've largely come to the defense of nVidia in this section, there is something which needs to be said to our readers. Midway through last year in an nVidia press meeting in Sydney, Australia we asked nVidia's Chief Scientist David Kirk if game companies would be required to release new patches for their game titles to take advantage of SLI and the answer was a clear and defined "No, all games will just work in SLI mode".Clearly though isn't entirely true as not all games currently contain profiles in the nVidia drivers to tell the game to run in SLI. We as hardware reviewers around the world expected SLI to just work for all games and in part we let our readers down in our initial preview of SLI technology expecting the aforementioned from nVidia and as some of our (and others) recent testing showed, not all games gain benefit from the extra graphics card.It was an ambitious comment at the time from David but let's just see what nVidia can do over the next few months with new driver releases as they are allowed more time to refine their SLI technology game support. Remember - progression over time!Setting up an SLI systemThere is more then just simply inserting the two graphics card into their own PCI E slot and having your SLI system up and running. For starters on the particular ASUS board we used there is a little module which looks like a SO-DIMM memory module that you have to insert the correct way so it makes use of both cards. Another thing is that the adapter (bridge) that goes across the top of the cards so that they can communicate together must be installed firmly.
While that sounds easy enough, when it comes to start installing the cards you can begin to get a headache as us and many have found. While we at first used the drivers that came with another brands retail cards that are SLI Approved, every time we changed the resolution when running SLI the system would crash. We ended up finally jumping across to some beta drivers (71.40) which finally gave us a clean and stable setup.
It's not that it's hard to setup but frustrating at times when you used official drivers that say they support SLI but far from work as you would expect.

SLI - Benchmarks - Test System Setup & 3DMark2001 SE

Test System SetupProcessor(s): AMD Athlon 64 3800+ Motherboard(s): ASUS A8N-SLI Deluxe (Supplied by ASUS) Memory: 2 X 512MB OCZ LL PC3200 2-2-2-5 (Supplied by OCZ) Hard Disk(s): Western Digital Raptor 74GB 10,000 RPM SATA (Supplied by Western Digital) Operating System: Windows XP Professional SP1Drivers: DX9c, nVidia 71.40 and nVidia 6.11 beta chipset driversWe will be testing the 6800 Ultra in SLI mode and in single GPU mode today. What we will be looking at which is something that we haven't seen yet is a few synthetic tests on how and if SLI affects performance of memory or CPU. We will be running the tests through our normal gaming benchmarks which include the 3DMark series as well as Half Life 2 and Doom 3. We will also have a look at what happens when we start bumping up the AA and AF and also finally our normal synthetic line up including SiSoft Sandra and PCMark.Our Performance PC article #2 will be coming in the very near future so we will be leaving overclocking of these cards till then. For now lets have a look if you could warrant the forking out of those extra dollars for a second 6800 Ultra PCI-E.3DMark2001 SEVersion and / or Patch Used: Build 330Developer Homepage: http://www.futuremark.comProduct Homepage: http://www.futuremark.com/products/3dmark2001/Buy It Here
3DMark2001 SE is a part of the popular 3DMark series. By combining DirectX 8.1 support with completely new graphics (including the GeForce4), it continues to provide benchmark results that empower you to make informed hardware assessments.
We can see here that SLI doesn't really give a huge jump in performance since 3DMark01 is quite CPU limited these days. We notice an increase when we start to overclock the processor but we will look at that another day.

SLI - Benchmarks - 3DMark03

3DMark03Version and / or Patch Used: Build 340Developer Homepage: http://www.futuremark.comProduct Homepage: http://www.futuremark.com/products/3dmark03/Buy It Here
3DMark03 is the latest version of the highly favored 3DMark series. By combining full DirectX9.0 support with completely new tests and graphics, 3DMark03 continues the legacy of being industry standard benchmark.Please Note: Due to recent events with the 3DMark03 series, we are adding results purely for those who are still in favor of 3DMark03. These results should not be taken too seriously and are only added for interest sakes.
3DMark03 starts making use of the graphics card more then the processor, while we don't see double the speed there is a significantly large gap between the single 6800 Ultra and two in our SLI setup.

SLI - Benchmarks - 3DMark05

3DMark05 Version and / or Patch Used: Build 110Developer Homepage: http://www.futuremark.com Product Homepage: http://www.futuremark.com/products/3dmark05/ Buy It Here
3DMark05 is the latest version in the popular 3DMark "Gamers Benchmark" series. It includes a complete set of DX9 benchmarks which tests Shader Model 2.0 and higher. For more information on the 3DMark05 benchmark, we recommend you read our preview here.
Just like 3DMark03 we again see a huge jump in performance between the single card and the two cards when running in SLI. You can see we get a little over double the performance.

SLI - Benchmarks - Doom 3

Doom 3Version and / or Patch Used: UnpatchedTimedemo or Level Used: Custom Timedemo (Alpha Labs 5)Developer Homepage: http://www.idsoftware.com Product Homepage: http://www.doom3.comBuy It Here
Doom 3 is the latest game to hit our test lab and is one of the most intensive games to dates. With our own custom time demo we are able to give a realistic rating on what kind of FPS you will be achieving.For more information on benchmarking Doom 3 we recommend you check out our extensive article regarding it here.
Doom 3 well and truly makes use of the extra graphics card, watching Doom 3 do a time demo at these speeds with its level of detail is really unreal.

SLI - Benchmarks - Half Life 2

Half Life 2 Version and / or Patch Used: UnpatchedTimedemo or Level Used: Custom TimedemoDeveloper Homepage: http://www.valvesoftware.com Product Homepage: http://www.half-life2.com Buy It Here
By taking the suspense, challenge and visceral charge of the original, and adding startling new realism and responsiveness, Half-Life 2 opens the door to a world where the player's presence affects everything around him, from the physical environment to the behaviors even the emotions of both friends and enemies. We benchmark Half Life 2 with our own custom timedemos as to avoid possible driver optimizations using the "record demo_name" command and loading the timedemo with the "timedemo demo_name" command - For a full list of the commands, click here.
While at the lower resolution we see vary little difference as soon as we crank it up to 1600 X 1200 we see absolutely awesome performance from the SLI setup.

SLI - Benchmarks - High Quality AA and AF

High Quality AA and AFAll tests were run with 4 times FSAA and 16 times Antistrophic Filtering enabled with the screen resolution set to 1024 X 768.When running these aggressive detail settings in 1600 x 1200, games really do become unplayable and if people are after image quality they will have to drop the resolution back down to reach playable levels.1024x768 was chosen as it is still the preferred playable resolution with these settings enabled.
You can see here that the performance jump is excellent when we start using AA and AF.
Again the performance jump is exceptional and just what we want to see. Let's have a look what happens in the real world when we start increasing image quality.
Moving away from the synthetic tests we still see an exceptional jump in performance here.
Half Life 2 was the only game that didn't really see any jump in performance at the lower resolution; we saw this when testing without AA and AF on as well.

SLI - Benchmarks - SiSoft Sandra

SiSoft SandraVersion and / or Patch Used: 2004Developer Homepage: http://www.sisoftware.co.ukProduct Homepage: http://sisoftware.jaggedonline.com/index.php?location=home&a=TTA&lang=enBuy It Here
SiSoft Sandra (System ANalyser, Diagnostic and Reporting Assistant) is a synthetic Windows benchmark that features different tests used to evaluate different PC subsystems.
We can see that system performance is barley impacted by SLI.

SLI - Benchmarks - PCMark 2002

PCMarkVersion and / or Patch Used: 2002/April 22nd PatchDeveloper Homepage: http://www.futuremark.comProduct Homepage: http://www.futuremark.com/products/pcmark04/Buy It Here
PCMark is a multipurpose benchmark, suited for benchmarking all kinds of PCs, from laptops to workstations, as well as across multiple Windows operating systems. This easy-to-use benchmark makes professional strength benchmarking software available even to novice users. PCMark consists of a series of tests that represent common tasks in home and office programs. PCMark also covers many additional areas outside the scope of other MadOnion.com benchmarks.
Again we see that performance of your system is not really affected with the addition of the extra graphics card.

SLI - Benchmarks - Conclusion

Conclusion Considering that SLI doesn't support all the programs we looked at it does give us at least a slight performance increase. Maybe the list of games you find back on page 4 would be better known as the games that are able to make full use of SLI, we can understand why nVidia didn't put a month of effort into making sure we saw a 90% increase in 3DMark2001 SE. They have worked on improving SLI efficiency in games that are probably the most popular at the moment and with the most popular games out the way they can start working on other popular titles and future titles.You can see for yourself that this is a very fast setup and anyone would be glad to have this running next to them right now. It's fast, surprisingly stable for a new technology and just totally kick ass to look at. With support for the major releases, people playing Half Life 2, Sims 2, Doom 3, Halo and more are going to see advantages and if you've made your way over to the Online Result Browser as of a late at Futuremark you can see that nothing is able to keep up with the power of two 6800 Ultra cards in SLI. nVidia aren't saying that this is for everyone nor are we but if you are serious about your gaming and you have some dollars to splash around, take the leap into the pond of SLI and we guarantee you won't be disappointed.You can see that SLI doesn't affect overall system performance in our line of synthetic tests so you aren't trading memory or CPU bandwidth for those extra frames. nVidia are on a good thing at the moment and you can tell that the Graphics Card King Crown title is back in their sight which they lost with the release of the 9700 Pro a few years back from ATI.You can complain all day long about the price of a top end SLI setup but there is no denying that two GeForce 6800 Ultra's in SLI is going to give you the best gaming experience around. This setup isn't for people with a 17" CRT or LCD that can only support 1280 X 1024. This setup is for people who own 21" CRTs that play at 1600 and above or Wide Screen LCD owners wanting to game at 1920 X 1200 without having to worry about having to drop to 16-bit or sacrifice a bit of image quality for a smooth frame rate. With an SLI setup you can play with it all turned on and still be smiling.While we would normally do a Pros and Cons section at the end of this final page we can simply say the Pros are everything about it - the look of two cards in a single system, the pure speed, the gaming experience, the satisfaction knowing that at this point in time your gaming experience isn't able to be any better and Cons, yeah it's expensive but so are Ferrari's and if you want the best you have to pay through the nose for it.The technology behind nVidia's SLI receives our TweakTown's "MUST HAVE" Editor's Choice award. Enough said.

Last updated: Apr 7, 2020 at 12:26 pm CDT

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Shawn takes care of all of our video card reviews. From 2009, Shawn is also taking care of our memory reviews, and from May 2011, Shawn also takes care of our CPU, chipset and motherboard reviews. As of December 2011, Shawn is based out of Taipei, Taiwan.

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