Enabling SLI and Cards with VRAM Discrepancies Options

[Exitios]

NOTICE: Recent drivers have been shown to exhibit a behavior that prevents a certain step from being completed.
THIS PROCEDURE CAN NO LONGER BE REGARDED AS A VIABLE OPTION.

This is for everyone that has two compatible SLI-ready graphics cards with differently sized VRAM subsystems, such as the 8600 GT 256 and 512 and the 8800 GTS 320 and 640, and would like to use them in SLI. 7800 GTX users should take note that it is not possible for a 7800 GTX 256 and a 7800 GTX 512 to be used together due to core optimizations made on the 512 version. First, the card with the smaller VRAM subsystem has to be installed in the primary PCI-Express slot. Second, download and install the CoolBits registry string, which you can download here. After installing CoolBits, open the Registry Editor and find the string. Once you've found it, set its value to 18 as shown below. Once that's done, you're set to enable SLI!

Note: Please remember this is not officially supported and this is merely a workaround. If this procedure does not work, please let us know.

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NVIDIA is aware of a certain behavior that is being exhibited by current and recent driver versions that prevents a crucial step from being completed. If you have two otherwise compatible video cards with differing VRAM sizes, please do the following:

• Download and install the CoolBits registry string, which can be found here.
• Open the registry editor and search for the CoolBits string.
• Double-click CoolBits and set the "Value Data" to 18.
• Once the value is changed, search your entire registry for "MB_SkipFBSizeCompare" without quotes.
• Please let us know if you do or do not see the aforementioned string, and also let us know what drivers (video and chipet) you are using along with relevant system specifications.

[datakill]

Hi

Thanks for the tip, but it doesn't work yet for me. Here is my story:


Config: CPU E6600 @ 3,3 Ghz (watercooled), MB Asus P5N32-E -SLI Plus (bios up to date)
2 Go ram Gskill
HD Raptor 150 Go
GFX: Zogis 8800 GTS 640 Mo (watercooled)
System: WIN XP

My brother offered me a MSI 8800 GTS 320mo.


What I did:

I moved the MSI gfx to the primary Slot

Using Nibitor and nvflash I flashed the Zogis gfx with the MSI gfx bios. It worked fine. My Zogis gfx match exactly the MSI card except one thing: It's still recognized as a 640mo card (seen in rivatuner).

Then I've found your tip using coolbits. As it didn't work, I reinstalled XP and its drivers, then did the coolbits tip again and it still does'nt work. Nothing appeared about SLI in the Nvidia control panel.


Any idea ?

This post has been edited by datakill: Sep 7 2007, 11:44 AM

[Exitios]

Alright, well, I've got a few questions for you.

1. What driver are you using?
2. Are your chipset drivers up to date?
3. With only one card installed do you see anything in the NVCP regarding SLI?
4. What wattage is your power supply?
5. Is the PCI-E broadcast aperture set to "auto" or "dual video card?"

[datakill]

Alright, well, I've got a few questions for you.

1. What driver are you using?
2. Are your chipset drivers up to date?
3. With only one card installed do you see anything in the NVCP regarding SLI?
4. What wattage is your power supply?
5. Is the PCI-E broadcast aperture set to "auto" or "dual video card?"

Thx for the answer

1. 162.18
2. Up to date
3. I tried that, nothing appeared
4. Seasonic - 650 W
5. I've seen nothing about SLI in the BIOS except for SLI overclocking. Also nothing in the MB manual talking about BIOS when instaling SLI cards. Should be all automatic.

[Exitios]

Have you ever seen the SLI option in the NVCP or had a bubble pop up notifying that your system is capable of supporting SLI?

[datakill]

Have you ever seen the SLI option in the NVCP or had a bubble pop up notifying that your system is capable of supporting SLI?

Nope, never seen that on that computer

[Exitios]

That's quite unusual, as many users actually complain that they want the SLI bubble to stop popping up. Are both video cards showing up in the Device Manager?

[datakill]

Yes, they show both in the device manager + Riva tuner. Even nvflash (under DOS) have shown them.

The SLI pop up for single card users was a bug in an older forceware version that have been fixed isn't it ?


BTW: I've found "SLI broadcast aperture" in the BIOS. Only 2 choices: auto and disable. It was set to "auto" from the start.




This post has been edited by datakill: Sep 7 2007, 01:39 PM

[Exitios]

The persistent notification issue has been resolved, but you should still get a "courtesy" reminder that your motherboard is SLI-ready. You should also be getting a pop-up balloon reminder when you install the second video card, and obviously that's not happening. Give the Beta drivers a try and see if it changes anything.

[datakill]

I tried the beta yesterday with the same result. I didn't talk about that, because it's just beta.

Looks like I tried everything

[Prohibition]

maybe flash the bios back to original. put 320 primary slot then 640 in the other slot. uninstall.. drive cleaner..reinstall 163.44..... my thoughts

[datakill]

If I do that, the cards won't match anymore because the MSI card is overclocked "in factory". At this moment the 2 cards have the MSI BIOS and then they run the same OC frequencies.

This post has been edited by datakill: Sep 7 2007, 04:18 PM

[Exitios]

The cards don't have to operate at the same frequencies; whichever card is installed as the primary usually forces its speeds on the slave card. Go ahead and give Prohibition's idea a try - he beat me to it.

[datakill]

On my way ;)

[datakill]

OK I did it, reflash the original BIOS on Zogis card, reinstall the drivers for beta, and the coolbits.

Still the same: nothing more

[Exitios]

Well, I don't have much more to suggest except for selling the MSI GTS and purchasing a 640 MB version. This isn't an officially supported function, and the CoolBits thread is a bit of a workaround, so it's not going to work all of the time.

[datakill]

Yep no problem, it was a hard challenge but at least I've learned to flash a GFX, some useful nflash fonctions and same for Nibitor. I got to see the good part of the things, and I guess this thread will be useful for others.

Anyway, I added the MSI card in my other computer instead of a SLI with 2 X 6600GT and on monday I'll purchase a SPARKLE 8800 GTS 640 Mo.

Kinda off-topic but tell me it will work this time


Thanks a lot for the fast support you provided to me. Thumbs up.


"Experience is a mean teacher - It gives you the punishments before the lessons"

[Exitios]

Now that setup will work. They're totally alike save the manufacturer and the VGA BIOS, but those don't matter in SLI configurations. Sorry about all the trouble you've had, but you've been a good example.

[Guloluseus]

Didnt work for me, either. Tried everything I couls think of, let some techs loose on it for a morning- nothing. Seems most people say it works, and anyone whos tried it says it doesnt LOL.

Maybe works for someone, but seems in th emajority of cases, not :(

[darkorb]

hi eveyrone

i have a XFX 8800gts Fatality 320mb, and a EVGA 8800GTS 640mb Superclocked.

i have tried everything, i mean everything. enable coolbits, try the GFX in different slots, tried what u recomended

nothing. i dont get SLI pop up, in bios everything is set to SLI/AUTO, and when its set to dual video card, it doesnt even boot.

heres my system.
amd x2 3800+ @ 2.7ghz
4xkingston 512mb ddr400 @ 450
ASUS A8N-SLI SE
Mushkin 650watt PSU
Seagate 500GB SATAII
Antec Atlas Case
22" LG Widescreen.

i honestly dont no what to do anymore