Per Nvidia: 2 9800gx2, 2 monitors, non-sli, not supported

[agoddard]

Hi,
I recently purchased the following system:

Operating System: Windows Vista Home Premium 64 Bit
Motherboard: EVGA 132-CK-NF78-A1 NF780I SLI
CPU: Q9450 2.66G overclocked to 3.2 gHz.
Memory: 8 gig OCZ OCZ2RPR10664GK
Video Cards: Two (2) MSI N9800GX2-M2D1G GF9800GX2
Hard Drives: Three WD 640GB 6400AAKS SATA 7200RPM 16MB. Two are in raid 0, with the OS installed on the raid array.
CPU cooler: XIGMATEK HDT-S1283
DVD Burner: LITE ON LH-20A1L-05 20x superallwrite SATA+lightscribe
Power Supply: ENERMAX EGX850EWL galaxy
Case: LIAN LI PC-P80B

My idea was to run one 24? monitor from the top PCIE slot and another from the bottom. I did not want to do quad SLI. Monitor resolutions are 1920x1200.

I spent about a week attempting to do this. I tried every way I could imagine to get this to work, and couldn?t. I could accomplish the following:

1. Get one 9800gx2 working in multi-gpu mode. 3dmark vantage score of about 10500.
2. Get one 9800gx2 working in multi-monitor mode. 3dmark vantage score of about 5500.
3. Get two 9800 gx2s working in quad-sli. 3dmark vantage score of about 15000.
4. Get two 9800 gx2s working in multi-monitor mode. 3d mark vantage score of about 5500.

It?s obvious from the above that:
1. A 9800gx2 with both halves of the card working together is about 10500.
2. A 9800 gx2 with only one half of the card working is about 5500.

I can?t get each card outputting to an individual monitor with each card performing in mult-gpu mode. I contacted nvidia support, and their answer is summarized here:

?I'm sorry but you cannot run two separate instances of Multi-GPU mode with two 9800GX2 cards. You can only disable SLI and be able to operate in a multi display environment or enable Quad SLI and be limited to a single display. What your trying to configure is not expected behavior nor supported.?

Ok, so nvidia doesn?t support what I?m trying to do. I won?t debate here whether I think that?s reasonable. So that leaves me with one super fast quad sli machine, or one dog of a multi-display system. I?d love for that to be somewhere in the middle.

Has anyone figured out a work around to help me accomplish what I want to do?
Is it possible to modify nvidia?s drivers to allow this?
Has anyone gotten the work around trick of adding a third cheap video card to work with 2 9800gx2s in quad sli?
Would the Matrox doubleheadtogo work for what I want to do?

I appreciate your time in reading this post, and look forward to some constructive replies.

 

[mhouck]

To take advantage of both gpu's on the GX2 you have to have the sli enabled in the control panel. It's my understanding that if you are running sli then you can't do a multiple monitor set up. So it's either run one GX2 without SLI enabled and use both displays or run both GPUs in quad SLI on one.

For your purposes you might try returning them for store credit or selling them and getting 9800 gtx, 260, 280 or the new 4800's from ATI. I think you are just out of luck. Sorry.

EDIT: sorry, forgot about your n780i board. Forget about ATI unless you want to get rid of your board too

 

[SergeC]

You're trying to run two separate instances of SLI on one computer......yeah, don't think anyone supports that - sorry.

 

[agoddard]

I've decided to RMA one of my cards. I wish it wasn't necessary, but as-is I can't justify keeping it around.