The Macintosh IIfx is very picky about its termination. At no time should
there be more than two terminators in the entire SCSI chain -- one on each
end, or in the case of only one internal SCSI hard drive, a single
terminator installed internally. All terminators used with the Macintosh
IIfx must either true IIfx-compatible or "augmented" by the IIfx SCSI
Filter (used only with internal hard drives).
In addition, older Apple Scanners had some additional capacitors installed
on the logic board, which may garble the SCSI signals when connected to
faster Macintosh computers. Install the Scanner driver version 2.0 to
correct this problem.