terminal command to boot in mirror mode

I need a terminal command that will either force OS X to boot from either 30 MHZ DP output or to boot in mirror mode. My 4K monitors get nothing unless I have an older DVI or HDMI input in the loop. I have a GTX980 TI running on external power in a Mac Pro that will not recognize 60 mhz Dell monitors at the low level boot screen or the full boot to desktop even though they are flashed to Mac. Every once in a Blue moon(every twenty odd boots) OS X does recognize the monitors at 30 mhz so I would think there is a command to force this every time.