P7001 capabilities?


I am curious if anyone knows off hand how useful the P7001 instrument is.
This seems to be a large GPIB/digitizer module which is inserted into the
midsection of a 7704A, creating an impressively immense piece of scope
hardware. It looks like it allows GPIB control of the mainframe functions
(but not the plugins--?), and has some A/D capability (for digitizing a
waveform I assume). Does the 7704A/P7001 equivalent to an early digitizing
scope, or is does the P7001 just give some automated control of the 7704A
functions? Would anyone care to compare it to, say, a 7854 or a 7K scope
with the 7D20 plugin?