CCMINER INTENSITY-
I have an Ubuntu 14.04.1 build, x64, and have had success with x13 and an intensity of 20.5. I have since tried various intensity settings with x11 and Lyra2RE algorithms. Algo x11 maxes out with "-i 20.5"' but the improvement is very small compared to the default intensity of 19, only about +25kh/s for the complete rig (6 x 750ti). Lyra2RE does not improve with an increased intensity, or a lowered intensity. With Lyra2RE, an intensity setting of "-i 21" or greater resulted in HUGE kh/s values and no accepted shares. Algos x11 and x13 generated "out of memory" errors at settings of "-i 20.7".
I have used the setting of "./ccminer -a x13 -d 0,1,2,3,4,5 -i 20.5,20.5,20.5,20.5,20.5,20.5 -o stratum+tcp://URL" in my launch string.
So, overall, x13 mining with "-i 20.5" gives +125kh/s on my 6-card rig (14,300kh/s), x11 mining with "-i 20.5" improves by 25kh/s on the same rig (17,900kh/s). For Lyra2RE, the intensity settings had little or no effect on accepted hash rate.
--scryptr
So you have to set intensity for each card.