My friend described one of those (a PPC640, not a PDP)
as a "luggable".
As in "you could probably lug it from place to place, but it's not
exactly practical".
Err, that also applies to a number of PDP11 models, and numerous other
computers :-)
IMHO the PPC with its fold-out full-size keyboard is impossible to use on
a lap. It's also not practical to run from the internal C-cell battery
pack (it takes 10 cells at a time and flattens primary cells in a couple
of hours). I use mine almst solely with that Microtest dist drive
aligment device I've mentioned in the past. I run it off the mains, from
a home-made PSU (I never got the ofifical Amstrad one).
-tony