Omega Engineering ISA RS-422 User Manual page 17

8. The following are known I/O conflicts:
The 278 and 378 settings may conflict with your printer I/O adapter.
3B0 cannot be used if a Monochrome adapter is installed.
3F8-3FF is typically reserved for COM1:
2F8-2FF is typically reserved for COM2:
3E8-3EF is typically reserved for COM3:
2E8-2EF is typically reserved for COM4:
OMG-ULTRA-SIO
Appendix A - Troubleshooting
Page 13