I have seen HP differentiate three levels of their PCL: level III, the
ThinkJet; level VI, the Deskjet; and level V, LaserJet+. I believe the Deskjet
won't accept softfonts. It has limited memory, but it allows font cartridges. I
think the memory is expandable. Each level adds additional features (i.e.
escape codes). You can generally use a driver for a lower level HP printer on
higher levels. The reverse doesn't always hold true. Any escape codes not
understood would be printed on the page and spoil the printout. I'll look for
more detailed information tomorrow and reply again.
-Greg