national instruments does provide GPIB driver support for linux for
their cards, which is not dependent on having a labview install. driver
appears to be available at no cost.
granted, this information probably isn’t much use. the manual for the
8640B is at: http://cp.literature.agilent.com/litweb/pdf/08640-90215.pdf
no GPIB option exists…was this instrument built pre 1974?
rick