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Can I Run Two Nvidia Boards In Sli And A Third As Stand Alone?


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Wierd question but...


Is it possible to run three nvidia cards on a tri-SLI board with two in SLI and the third driving a second monitor as a stand alone? For example, could I run 2 gtx260s in PCI-E slots 1 and 2 in SLI and a 8800GTS in PCI-E slot 3 as a single card to drive a second monitor?


Please pardon if this is an inane question but it will have some impact on my setup decision. I am contemplating either a single gtx 280 for gaming and a 8800gts for the second monitor (have one) or the above three card solution. I don't want to lose my second monitor but the price differential between two gtx 260s and a single gtx 280 is only about $200.


Yes..heat production and power consumption would be ferocious on the three card solution. I will have the CPU and NB on a separate water loop and cool the cards on air for now. Would consider an upgrade to a second water loop for the cards later but, frankly, this seems like a very costly and questionable yield option.



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XP or vista? if XP it MIGHT work. Though no amount of beating it with a stick would get my 8800GT SLI and 6800GS combo working for the same intent. It kept telling me the 6800GS wasnt capable of going in SLI with he GTs...ummm yeah knew that. In XP however the soluion waseasy, slap an ATI card in and go, it wont try to SLI with that :)


Vista was another story. Same XP issues plus it requires all video cards to use an identical driver, so no ATI/nvidia mixing and no mixing of certin cards fromthe same maker. Allegedly this is only with Aero enabled, yet I ran into the poblem in every way shape and form to the point I sad screw it and went to a single LCD for gaming, which royally pissed me off on top of the other Vista nonsence. So back to XP x64 and and ATI card doing the extra work for me. Both are crappy "solutions" to what shoudnt even BE a problem.

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- I take no responsibility for your computer hardware nor software if you decide to follow my guide - Do it at your own risk!

- Multiple Monitors when SLI is enabled are not supported in any way by Nvidia when this guide was written.

- This guide is written for the 169.25 drivers but will most likely work with any driver.




I have read a lot of threads in this forum about how to run multiple monitors when SLI is enabled. And it differs from thread to thread and I don't think the solution I found has been mentioned earlier (but I could be wrong). Actually I was thinking about this "trick" before I decided to tested it and before I asked in here, and when I got the time to test it, it actually worked right away. I was afraid that my trick would be reset after a system reboot but it didn't which makes this solution perfect in my eyes.


One way to use multiple monitors is to use an adaptor, but this adaptor will just tell your graphics card that all your monitors are one big monitor and due to the large resolution the game performance will be much worse than playing on one monitor. The other way to run multiple monitors is to have another graphics card not running in SLI to handle the other 1-2 monitor you would like to connect, and let the SLI-cards handle the primary display. And this is very confusing since some people seem to have succeeded while others didn't.


It is said that an ATI-card combined with 2 Nvidia Card in SLI will work in Windows XP but not in Windows Vista because Vista doesn't allow two different video card drivers and unfortunately I haven’t been able to test if that's the case. But I will try ATI in Windows Vista later, but I don't have access to a card at the moment.




Requirements for this Guide

There are a few requirements to be able to succeed with this and those are:

2 Nvidia Graphics Cards running in SLI

1 other Nvidia Graphics Card (PCI or PCI-E)

Windows Vista (32bit or 64bit)

This guide has only been tested on Windows Vista. Some replays in this thread report about problems in Windows XP and that it's not working.



The Guide

The two cards running in SLI will handle the main monitors which you would like to use when you play games or other graphics hungry applications. This is exactly like the same as before. The second monitor, or even the third if you have a total of three monitors, will be connected to the other graphics card not running in SLI. Make sure you do these changes before you continue.


Also make sure you disable SLI, if activated and have all three cards installed in your computer before continuing.


When you start your computer with two similar cards and another Nvidia graphics card, you will not be able to activate SLI. I think Nvidia detects that all graphics cards are not the same and have no working SLI bridge between them and automatically disables it. But don't worry, we will activate it anyway!



If you open your Display Settings, it should look similar to this:



There should be 6 "monitors" to attach if everything is correct so far.



Now go to Device Manager by right clicking on "My Computer" or "Computer" as it's only called in Vista and click "Manage". Click on the Device Manager and expand your "Display Adaptors". Now Disable the graphics card that you are not going to use in SLI. In this example it's 8600GT since the two 8800GTX will be used in SLI.



You will get a question asking you if you really want to disable it, but for this guide to work it's required.



- Restart your Computer




Now when the computer has been restarted, you can activate SLI in your control panel.




And you should restart your computer after enabling SLI, even if you didn't need to.



- Yes, restart the computer...




Now the other graphics card that you disabled in Device Manager should have been enabled again automatically, if not enable it yourself.


Then go to Display Settings again and it should look like this now:



You can attach the other monitor(s) now and expand your desktop.


The SLI graphics cards are using the main monitor together, like they should in SLI-mode. And the other graphics card can handle the other two monitor(s).


Proof that it actually works with 8600GT:

Screen shot (Original Size)

Screen shot (Medium Size)

Screen shot (Small Size)


Tested with DirextX applications (CS:S and 3DMark06) and it works.


Proof that it also work with another series (7100GS):

Screen shot (Original Size)

Screen shot (Medium Size)


Tested with DirextX applications (CS:S and 3DMark06) and it works.




Hope this helps and Good Luck!


Edit1: Added proof that it also works with two different Nvidia series.


This post has been edited by FredrikMH: Feb 11 2008, 06:50 AM

(from NVidia SLI Zone, linked from XS)

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Hey, that's super help. Sounds like something to try. Now I just need a portable nuclear reactor to run two gtx 260s, an 8800 GTS, various hard drives, pump, etc.... Thanks again for the detailed information.

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What do you think concerning power...


1000 W power supply.


2 x gtx 260

1 x 8800GTS 512 G92

Motherboard with Q6600 B3 clocked to 3 Ghz

Pump for water cooling

6x 120 mm fans

multi fan controller

DVD RW optical drive

2 SATA drives (including one velociraptor)


Enough power? Do I need to add another powersupply to this build (I have a 550 W lying around)?

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Go for a single rail PSU for running 3 cards so you will not have a problem with overloading a 12V rail...


For that system, I work it out to use ~72W more than me


GTX260 SLI vs 8800GTS SLI ~= +115W

8800GTS vs USB-DVI ~= +117W

2 HDD vs 10 HDD ~= -160W


Overall ~= +72W


My max is 563W DC... so... 635W DC for you... a PCP&C Silencer 750 would still easily do your rig... with the current price of this PSU, I find it hard to recommend anything else apart from maybe the PCP&C TurboCool 860... but the fan in the PSU might annoy you, it's a Delta... I have to change the fan in my PCP&C TurboCool 510 some time because it's the most annoying sound of all the fans in a whole system lol... I guess if you wanted more headroom above ~635W for future additions, someone else can come up with suggestions for >750W silent but powerful PSUs


The PCP&C Silencer 750 "only" has 2x PCI-E 6pin + 2x PCI-E 6+2pin, so you'd have to use a PCI-E 6pin to 2x 4pin Molex power adaptor cable for the 8800GTS, but with 60A on the 12V rail it won't matter at all...

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Yeah, once you go past 4 PCIe power connectors you are getting into serious power supply territory (as in generally 1KW+ units).


The fact that you can pick up a PCP&C 750 for as little as $120 (with rebate) makes it very competitive and I would certainly expect it to handle such a setup.


There are some very good PSUs in the 'more than 4 PCIe connectors' category, such as the Corsair HX1000, but you are looking at considerably more money there.


Silverstone are the only company I can think of off the top of my head that put more connectors on PSUs under 1KW, but they tend to have four 6-pin types, then solid 8-pin types (not the 6+2 connectors), which makes them less useful in this situation.

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Here's my set-up:


8800GTS SLI @ 1920x1200

7800GT @ 1680x1050




I was previously using a USB-DVI adapter for the secondary monitor, but the driver only currently support XP and Vista 32-bit... so for 64-bit I needed to mod my old 7800GT to silence it and squeeze it in between the 8800s... it's jam-packed in there now lol... good job the 88s are on water else they be choking :lol:



I tried this trick in XP and it didn't work for me... I don't think anyone has got it working in XP... So it's back to USB-DVI for XP :lol:


So now I have 7 DVI ports and 2 monitors lol

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