I have a geforce gtx 1070. I mine ether for test. I got a hashrate of 25. mhs and it uses just 15 percent of my gpu.
So ist possible to mine different currencies on the same time with one graphic card?.

The second question is if I would put another graphic card like the gtx 1080. But dont use sli would it increase the hashrate the same? Or would it be possible to mine with one card for example ethereum and with the other zzcash?

Perhaps somebody can answer the question here