Hello,
That is correct. At this time, GPIB is only supported on the 8146 RT and 8156B RT controllers. LabVIEW RT does not support the GPIB controllers on the 8175 and 8176; also, PXI GPIB cards are not supported.
There are a few easy alternatives to using the ethernet link. One easy solution is to use your serial ports. Another solution is to use your I/O modules, like Analog or Digital lines on a Data Acquisition board to share information between systems.
I hope this information helps.
Regards,
Dafna