I recently add a GTX 780 to a machine with a 770 and a 690, and the GK104 cards, despite correctly installed,are not in use by BOINC. BOINC says "not in use". I recall something about BOINC chosing just the fastest card on a machine and ignoring others. There is any command that I must add to cc_config or something?

If it chose just the fastest card, only the 690 would work. I am personally not the most informed on this topic. But I'll do some digging in case no one answers first.

<use_all_gpus>1</use_all_gpus>in the "options" section of the config file, stop and restart BOINC.

first thing I found.

Yeah, I will try that and let you know. In fact it seems boinc choose the fastest GPU, not "card", by the measured GFLOPS

<use_all_gpus>1</use_all_gpus>in the "options" section of the config file, stop and restart BOINC.

first thing I found.

Will do. But yesterday I receive a distress call from my SETI group, GPUUG, and they are needing me for a bit of time. So I will take a break from GPUGRID (sadly), but will keep improving my hosts, and by the time im back, it may be for another couple of years season.
Keep on the good crunching works guys, we really need medicine improvements. Best regards to all of you.

FireHawk, that host of yours with the 690 and the 770 is interesting as 690's times are quite close of 770's. Could you post the spec of both cards?. Thanks.

Btw, sad that you leave GPUGRID

The time are closer because the 690 runs with 1160mhz at GPU and a 600mhz memory overclock. pretty close to the stocks setting of the 770, hence the close times.