I have one GTX260 at present processing and getting ready to get a 2nd one for the same pc.
My question: is would it possible to disable one of them temporarily for another purpose and if
so how is it done or would I need to shut down boinc altogether ?

By default Boinc 6.20.xx sumthin' err other will only use one GPU.

To enable the other one you will need to add the following line to your cc_config.xml file in your Boinc data directory.

<use_all_gpus>1</use_all_gpus>

Here is a template file that can be pasted into notepad and customized for your application. After you type the number of concurrent threads you wish to run (number of logical processors+GPU cores); save the file to your C:\Documents and setting\All Users\Application Data\Boinc
Ensure it is saved as a .XML file and not .txt When you sish to disable the second GPU change the 1 in the line above to a zero.

<cc_config>
<options>
<ncpus>NUMBER_OF_LOGICAL_PROCESSORS+NUMBER_OF_GPUs</ncpus>
</options>
</cc_config>


Good luck and congratulations on the new card!

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"The most exciting phrase to hear in science, the one that heralds new discoveries, is not Eureka! (I found it!) but rather, 'hmm... that's funny...'" -- Isaac Asimov

Actually, that's only the 6.4.x series that you need to add the <ncpus> in your cc_config.xml file. BOINC v6.6.20 has that fixed already. In fact, if you have <ncpus> in your cc_config.xml file with v6.6.20, you should remove it to avoid problems.

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