This is not a big deal but I did not like the bare third PCI express slot so I bought a 220 just to occupy it and run a bit more CUDA BOINC. BOINC only found my two 260s and would not pick up the 220. I reinstalled BOINC and tried the 260s in SLI mode and SLI disabled but BOINC would not report finding the 220. I took out the 220 and put it in a spare PC and it worked fine there. This is not an issue of BOINC not using the third (220) card it just did not find it in the boot messages. Windows found it and loaded drivers fine.
Windows 7 64 bit Ultimate
4 GB Ram

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I think you'll need 3way sli and same boards to run cuda on all of them. 2x260&1x220 wouldn't work as far as I know. Give it a try :)

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Hmm.. maybe..

I have no knowledge with Win7..

* Make a cc_config.xml: [http://boinc.berkeley.edu/wiki/Client_configuration]
..like this:
<cc_config>
<options>
<use_all_gpus>1</use_all_gpus>
</options>
</cc_config>

..maybe also..
* Extend the WindowsDesktop to the 3rd GPU.


SLI 'disturb' CUDA crunching, so disable it (it won't give more performance - the contrary, it slow down).
But IIRC the new nVIDIA_driver disable SLI automatically if CUDA crunching is detected.

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