Guru 3D SLI Users Guide

Discussion in 'Videocards - NVIDIA GeForce' started by MikeMK, Jan 18, 2005.

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  1. MikeMK

    MikeMK Ancient Guru

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    I have noticed over the past couple of weeks that more and more people are starting to consider SLI as a viable option, so I thought it would be useful to start this thread so we can all help each other out. Basically, this is a place to post your experiences - drivers, benchmarks etc, and for ppl considering whether or not an SLI rig is worth it, to come and get some answers.
    I shall start off with some basics, but feel free to add stuff from your own experiences.

    Supported Hardware

    Motherboards:

    Basically, the only motherboards that support SLI at the moment are Nforce 4 based boards. All the major motherboard manufacturers now have SLI boards available. You can find some reviews here for Gigabyte, and here for Asus. And here is a general look at Nforce4. DFI have now released their rather tastey looking SLI board, and now you can get their updated SLI-DR Expert board, which has much better board arrangement and extra space between the PCI-E slots. Particularly useful if you are intending to watercool. MSI have one on the market aswell. Here is a great test of all four boards from anandtech. And for further comparason, you can find another group test HERE. Nvidia have also launched Nforce 4 16x, which allows both PCI-E lanes to provide 16x to each card, rather than 8x each on standard Nforce 4 boards. One of the first boards to market was the Asus A8N32-SLI Deluxe, of which you can find a review HERE.
    As of the 6th April 2005, Nvidia have launched their Nforce 4 Platform for Intel CPU's. Therefore you are now no longer limited to choosing an AMD system if you want an SLI rig. The Nforce 4 Intel edition seems to be holding out well compared to other intel based chipsets. One thing to bear in mind though is that for some reason they dont support the Pentium D 820 CPU's, although they do support all other Pentium D chips. HERE you can find a review of MSI's P4N Diamond, and Gigabytes GA-8N SLI Royal, and a general overview of Intel Edition SLI can be found HERE

    Graphics Cards

    Virtually the full range of nvidia cards from the 6 series - 6600 through to the 6800Ultra - right through to the 7 series, - 7600GT to the top of the line 7900GTX - supports SLI.
    One exception to this though is that 6800GTO's (cut down 12 pipe version of the GT) DO NOT Support SLI, and while it will recognise them as SLI capable, linking two together results in massive Graphical corruption, as one Guru3d member unfortunately found out!
    One other thing to bear in mind, is that at the moment, SLI has NO dual monitor support, therefore you can only use one monitor in SLI mode.
    The most important thing to bear in mind is that any hardware you buy has this:
    [​IMG] stamped somwhere on the box.
    If you are concerned about compatability of your Graphics cards, have a look at nvidias SLI site HERE

    For your your reference, you can find review for the following SLI setups.

    7900GTX/GT & 7600GT - HERE, HERE and HERE

    Here are Guru3d's very own SLI findings. Firstly, 6600GT SLI, secondly, a review of Gigabytes interesting dual GPU card, the 3D1 and finally, by dual 7800GTX and 7800GT's

    There has also been a few misconceptions as to compatibility, and which cards can be used together. It used to be the case that you had to have 2 identical cards with same bios and from the same manufacturer. This is now no longer the case. Nvidia has updated their drivers so cards will work with different bios's, and they now no longer have to be from the same manufacturer. Therefore you could use a 7900GT from XFX with one from BFG if you wanted to. However, please note that if you are using 2 pre-overclocked cards (or one pre-overclocked and one stock) in SLI mode both cards will run at the speed of the slowest card. i.e. the faster card will be downclocked.

    Application compatability

    Much has been made of the fact that SLI will only work if there are 'profiles' for a game present in the drivers. You can find the list of officially supported apps here There are now at least150 or more applications that support SLI including benchmarks. However, it is no longer the case that you are stuck with single card support if there isnt an 'official' profile, as Nvidia provides you with the tools you need to create your own SLI profiles, including the ability to choose SLI rendering modes, for all your games within their drivers. You can find instructions on that here. Performance will vary from game to game, and depending on which rendering mode you use. Bear in mind that older games may not benifit from SLI due to CPU limitation.
    It is directly because of this that nvidia have added additional AA support as an SLI rendering mode to take advantage of games CPU limited in SLI mode. This gives you the option of utilising that graphics horse power for better IQ where higher FPS may not be necessary. There are currently two AA modes. SLI 8x and SLI 16x. These should work on ALL games and are available in drivers from 77.76 onwards. You can find details on how this works here
    Note - There is a bug in some games 'in-game' screenshot function, and with apps like FRAPS that take screenshots, as they take the shot before the final image has been composited and output to your monitor. Therefore screenshots will not necassarily show SLI AA as being applied. The only way currently to ensure you get a screen shot with SLI AA applied is by using PRINT SCREEN key on your keyboard. So dont panic if you screenshots dont look as good as you expect!


    There are also third party applications now becoming available for people to set SLI profiles for themselves. One such app is nhancer developed by Guru3d member Grestorn and looks like a very promising little app. I have been using it and it works very well, enabling SLI in all games I tried it on, although I must say that performance increase varied greatly from game to game as with using profiles in the drivers. Also note that some games prefer one rendering mode (i.e. SFR or AFR) over another. For example KOTOR II would crash with AA and AF enabled on SFR, but runs fine with AFR. I recommend you give it a try and see what works! As well as SLI profiles, it also lets you edit all your game profiles in a much more user friendly way than the nvidia CP.

    If you want to see what effect SLI is having on your games and how its distributing load between the cards, you can enable 'load balancing' under the multi GPU tab in the drivers. This will display green lines that divide the screen into two areas, one for each GPU. Please note, that some people have been confused by this as it occasionally set to 'on' as defualt, so if u see green lines over your games, dont panic... just disable load balancing!

    Is SLI for you?
    As with all new technology, it is best to go into it expecting to fiddle, tweak and hone to get it all set up and working as you like. Things obviously improve as they gain more support. Having said that, i was impressed at how easy my system was to get going.
    There are two real reasons for investing in SLI.
    1) to get next gen performance NOW. This is the expensive option, and one only for die hard enthusiasts with the money to spend (like me! ;) ) The biggest thing to remember if you are investing in 2x7800GT/GTX's right away is that you will need a CPU to match. Even a top of the line FX57 will bottleneck these cards, so bare this in mind. The main advantage to this is that you will not need to upgrade for a VERY long time. The CPU issue has become a little more complex with the addition of dual core CPU's to the market. Please bear in mind that if you are building a gaming SLI rig, then you will see no benifit from dual core CPU's in games. Infact, a top of the line X2 4800+ will only perform similar to a single core 4000+, and costs around the same as an FX-57. Depending on what your building your rig for, the FX-57 may be the better bet if gaming is your primary concern, or you could save some pennies and get a 4000+ as you would experience the same in game performance as the X2 4800+.

    2) As a basis for an upgrade platform. With PCI-E, socket 939, and all the other features of Nforce 4, it makes a very good basis for a system that can be added to in the long run. For example, you could buy one card now, and then double your performance on the cheap at a later date. This works particularly well for the more affordable 6600GT, although bare in mind if you intend to get two of these it might be better to invest in a single 6800GT as it leaves you with more options in the future, although this depends on cost. If you intend to go down this route, make sure both cards are compatible.

    Power
    While an SLI rig may provide you with the ultimate in gaming power, bear in mind it is also going to require the ultimate in electrical power. One of the most important things to think about when upgrading to SLI is a decent powersupply. This is particularly important when 2 6800GT's/Ultras are thrown into the equasion and even 7800GT's/GTX's even though they have slightly lower power consumption.
    Make sure its from a decent manufacturer, like Antec, Enermax or OCZ, and that the Amps on each rail are extrememly good. An ATX 2 compliant PSU is also a definate plus if you can get one For reference, I am running on an Enermax 600Watt Noisetaker, with 2x12v lines at 18amps each. It is totally stable so far, but then you would expect it from that level of PSU. I recommend a minimum of a 500watt PSU with at least 30amps on the 12v rail for those using high end cards (i.e. 6800GT or higher) in SLI configuration.

    Monitors & Screen Resolution
    If you are considering an SLI system, especially a high end 7900GT/GTX based system, it is essential that you consider your monitor. Particlularly in the case of TFT's. Bare in mind that you really will not see the benifit of a SLI rig at this level running at anything less than 1600x1200, due to CPU limitation, and really the only advantage would be higher benchmark scores. All that power will just not be used on a 17" TFT with 1280x1024 native res, and i would consider a resolution of 1024x768 a complete waste!!!
    Basically, if you arent bothered about benchmarks, and can only run at a resolution no higher than 1280x1024, dont expect to be 'blown away'. Maybe consider a monitor upgrade and a single card in the short term, you can always add a second card down the line.

    SLI Rendering Modes

    When setting your own profiles in the drivers (or 3rd party app if you choose) there are various different rendering modes available. Some will work better than others depending on the game. Here is a quick rundown on the modes available. See the link above (under application compatibility) for details on how to setup your own profiles.

    SFR (Split Frame Rendering) - basically, the the top portion of the frame is rendered by one card, and the bottom by the other. This isnt a 50 50 split, but is measured 'on the fly' so, say sky doesnt need as much power to render, so the card doing this may do 60 or 65% of the frame, and the card rendering the bottom half, (the more detailed floor) would do 35%

    AFR (and AFR2) - Alternate Frame Rendering - basically all odd frames are rendered by one GPU and all even frames rendered by the other GPU. I havnt been able to find out exactly what the difference is between AFR and AFR two - I think its just a compatilbilty adjustment.

    SLI 8x & SLI 16x Modes - Applies 8x/16x AA. In 16x AA mode both GPU's render the SAME frame, and apply 8x AA to each, but off set (i.e. applied at different points) the image is then composited creating 16xAA on the viewed frame.

    Auto-Select - Does exactly what it says, auto selects the rendering mode. For all games with official SLI profiles, it will default to the rendering mode defined in the profile. Other games will run in single card mode unless u have created a user profile stating otherwise

    Multi-GPU - All games are rendered in SLI, in SFR mode. Official Profiles over-ride this where necessary, as do User defined profiles.

    Single Card - Well... a bit self explanitory really!

    Overclocking in SLI mode

    Overclocking in SLI mode is just the same as with a single card. Whether using Coolbits or Rivatuner, only ONE set of Core and memory speeds will be displayed. Dont worry, this is totally normal. When you overclock either the memory or core clock slider it is overclocking BOTH cards. The reason you cant see two sets of controls (one for each card) is because clock speeds have to be sync'ed for SLI to work properly. If there were a set for each card, you could run one card at a different speed to the other, leading to possible stability issues.
    One final note. Riva Tuner will only display clock frequencies and temp values for the primary card, and not the secondary one. Again, this is normal. When you overclock using Riva Tuner you are automatically overclocking both cards.

    Monitoring Dual GPU temps for LCD displays/Rivatuner/MBM5

    As you may be aware, Riva tuner doesnt support temp monitoring for both GPU's, so the only way you can monitor this, is through the Nvidia CP. However, there is a work around using Motherboard Monitor 5 instead of Rivatuner.You can monitor both ambient and core temps like this, and even send the data to an LCD screen like the Matrix Orbital for BOTH cards seperately. You need to grab a copy of Motherboard Monitor 5, and mod it to recognise nforce 4 motherboards. Its quite simple really... see HERE.

    And see here to see how to get MBM5 to recognise SLI temps on the 2nd GPU see HERE.

    You dont even need to run Riva Tuner at all now, just MBM5 instead. Once you have set all that up, and if you are lucky enough to own one (like me ;) ) you can use a plug in to your LCD software (im using LCDC with the MBM5 plugin and it works great) to program screens and display the temps on your front panel LCD screen. It works great and allows you to monitor your GPU temps for both graphics cards while gaming.

    Hope this gives you a good starting point, but remember now for the first time SLI has some competition from the most recent iteration of Crossfire. If you are spending so much money on your rig, its worth considering all the options, so head over to my 'Crossfire Users Guide' and see which you think is the best option for you!

    Hope that helps.

    Over to you guyz
    Thats enough of me banging on, so its over to you to provide your experiences, or feel free to ask questions. I am particularly interested for input from those of you with 6600GT's/vanilla 6800's as most of the issues I have seen with SLI have been to do with these cards. These are also the level of system that I think will become most popular as they are more affordable. Feel free to post benchmarks, driver and hardware recommendations, overclocking results and any tips that you have regarding SLI
     
    Last edited: May 7, 2006
  2. stefanovicho

    stefanovicho Maha Guru

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    nice :) post you go there m8 :D
     
  3. Marley

    Marley Don José Cuervo

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    Nice guide, Stickied ;)
     
  4. McGeyser

    McGeyser Active Member

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    MikeMK,

    I see that games need to have driver support to get the benefit of SLI. How about intense 3D and Animation applications? Will SLI function seamlessly with 3DStudio Max, Maya and the Adobe lineup? The system I am building for a client is primarily for these reasons, he likes games too, but he needs serious rendering power. I know Unwinder has added 6800 GT> 4000 Quadro conversion, but that negates SLI function correct?
     

  5. MikeMK

    MikeMK Ancient Guru

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    No, SLI does not support 3D animation etc, not unless Nvidia actually add support to those apps. Atm, it is being developed primarily as the ultimate gaming set up, so, for example, there is no Dual monitor support when SLI mode is enabled. Basically, for gaming, SLI rocks, for 3d/animation apps you are better off with a pro card like the Quadro.
     
  6. Maestros

    Maestros Guest

    Excellent. Great info. Thanks.
     
  7. McGeyser

    McGeyser Active Member

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    Ouch, the truth hurt MikeMK. I should have done my homework.

    How can SLI be deemed scalable at this point. A truly scalable setup would function regardless of application, the hardware should scale to task, for the name's sake. I am going to have some explaining to do for this one.

    When you say SLI won't work for these apps, what does that entail? Memory errors or black/blue screen?

    This is where my misconceptions were born
     
    Last edited: Jan 18, 2005
  8. MikeMK

    MikeMK Ancient Guru

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    No it will work, you can run the apps no problem, it will just default to the primary card automatically, so it will be like using one graphics card instead of 2 in those applications. I have noticed some performance boost in games that dont officially support SLI, so you may be lucky, but this performance boost isnt as much as the ones that support it fully. It should be 100% stable though. I dont use the applications you are refering to, so I cant really say for sure how they will run.

    EDIT: I should add, that in apps that dont support SLI, you actually get a small performance drop. This is down to the CPU overhead of managing both cards. For example, with a single card in non SLI i score 24,500 in 3dmark 2001, but with 2 cards I get about 23,500 - this is because 3dm2k1 doesnt support SLI.
     
    Last edited: Jan 19, 2005
  9. McGeyser

    McGeyser Active Member

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    When you disable SLI in the control panel, do you have to reboot or will multi display function immediately? Thanks for your reply's MikeMK.
     
  10. MikeMK

    MikeMK Ancient Guru

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    You wont actually need to disable SLI for the apps to work. Just run the application, and the PC will sort out the load balancing. If the application doesnt support SLI, then all the load will be put on the primary graphics card automatically. It will seem just like using the application normally, but with one card, not two so u dont get the performance boost of SLI.
    If you did want to disable SLi, then yes, you would have to reboot.
     

  11. AJ²06

    AJ²06 Ancient Guru

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    Nice post. Informative. SO does SLi split the 16x PCI Express bus into 8x8 or whats the deal?
     
  12. MikeMK

    MikeMK Ancient Guru

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    Yes, thats correct. The PCI-E graphics ports share the 16x lanes, so when you have two cards in parrallel it splits it down to 2x 8x. This isnt an issue at all, as current GPU's dont even utilise the full bandwidth of PCI-E 8x, so its an efficient use of the PCI-E bus.

    EDIT - should have mentioned this in the original post! LOL!
     
  13. SamHughe

    SamHughe Master Guru

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    How much did the whole thing cost you?

    SamHughe
     
  14. MikeMK

    MikeMK Ancient Guru

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    I have just added a new link in the guide to an interesting article brought to my attention about application profiles. Worth a read.
     
  15. AJ²06

    AJ²06 Ancient Guru

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    Thanx 4 da answer... :thumbup: AND how much was this beast...? :D
     
    Last edited: Jan 20, 2005

  16. McGeyser

    McGeyser Active Member

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    To answer the pricing question, here is a system built for a client:

    All but video cards were purchased from Newegg.

    269.99 Asus A8N SLI Dlx
    137.00 1024 Mushkin Enhanced 2.5
    130.00 ChenMing case and 520W Aspire PSU
    20.00 2 4 pin molex to 6 pin PCIe power adapter converters
    199.00 AMD 3400 2.2GHz 939 CPU - OEM
    42.00 Zalman ALCu 7700 120MM CPU fan - this thing is HUGE!! 27C idle
    Client is providing drives HDD's and DVD

    $885 delivered and tax 1/15/05

    Ebay 2 X 6800 GTO GT's

    $895 delivered

    Grand Total $1790

    Had the client needed drives, the total cost would be nearing the $2200 mark.

    EDIT: I would think with an FX-55, faster RAM, alum. case w/ HP PSU, and Raid Raptors you are looking at more like $3300. Am I close MikeMK?
     
    Last edited: Jan 20, 2005
  17. MikeMK

    MikeMK Ancient Guru

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    Well, in £'s this is how much it was:

    PCI-E GT's = £330 each
    A8n SLI deluxe = £140
    FX-55 = £555
    PSU (Enermax 600Watt) = £88
    - The rest I already had from my previous system and have built up for a while, but would cost something like this now -
    WD Raptors (36gb) = £75 each
    200gb WD - £70
    OCZ PC3700 = £200
    Case (TT Xaser III) was £100 18 months ago
    DVD Rom and DVD Burner = £80 between them.

    Total = £1968, so about £2000 really. Not sure what it is in USD.

    McGeyser - Go check that link i mentioned in my last post. It could help you with your 3d animation issue. Im not sure if it would work, but u might be able to set up your own application profile for those applications. Worth a shot I think!
     
    Last edited: Jan 20, 2005
  18. McGeyser

    McGeyser Active Member

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    Good info, thanks MikeMK. I will have try this, I'll post back with results. It might take until saturday. Thanks again.
     
  19. MikeMK

    MikeMK Ancient Guru

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    No problem. Will be interested to hear if it works!
     
  20. Liranan

    Liranan Ancient Guru

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    The nForce 4 is not the only chipset that can support SLI. Gigabyte have released a motherboard based on the 915 chip for Intel with SLI support, so now even Intel users can have SLI setups.
     
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