I started milkyway on my new box with 3x5870, but constantly have only 2 task in progress, so I can use only one or maximum two gpus. On the other box everything is ok, but on the new one it`s problem. As I can remember sheduler has to give 6 tasks per gpu?

I do believe that you will need the use all GPU option in the config,

<cc_config>
    <options>
        <use_all_gpus>1</use_all_gpus>
    </options>
</cc_config> 

You might also need the dummy plugs, but try the cc_config option first.

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