Waterfall displays are very expensive, and for a SETI station to be
really useful, it should be operating 24x7 and rarely being watched.
An X waterfall is even worse.
Specgram2, with some small changes to remove floating point operations,
spends the majority of its time maintaining the display, even when
using the relatively efficient SVGA library interface. That time could
be better spent in more sophisticated searching algorithms.