oclhashcat without a monitor

hi to all
is it possible to run the oclhashcat without plugin a monitor.
I have tried oclhashcat with --benchmark and it was okey when monitor is plugged.
But when we move the PC to server room without a monitor plugged (even no kvm)  oclhashat give me the following error when I connect with ssh -x ipadddress

ERROR: clGetDeviceIDs() -1

Is there any solution for this?
Any idea?

REgards...