On my 5.0a board, you physically remove the terminators. On a 5.1 or 6.0 board, you can do it via scsi2sd-util. On the 5.5 board, the web site says it is permanently enabled. http://www.codesrc.com/mediawiki/index.php/SCSI2SD#Technical_Specifications
Note there is a comment for the 5.5 board...