Truly, I don't know what that means.  Oh and major error on my part - it's ***80-pin***, I apologize.

I googled the P/N (313706-B21), and it's confusing as to who actually manufactured this drive and possibly who slapped their name on it.  In any event, I googled that with "differential" and I can't find any evidence of an overlap.

But as I said, I don't really know what that means.  Low-voltage differential?