Presumably you're using a 1.2 kernel then?
The scrollback used to be done as nothing but a side effect of the
way the scrolling was done: scrolling up by one line is accomplished
by moving the start-of-screen pointer *down* by a line. This allows
everything from the top of VRAM to the current screen position to be
used as scrollback, at no extra cost. However, if you try to get
scrollback *just* after the screen position has had to be wrapped
back round to the top, you don't get a lot of it at all.
>From 1.3.3 onwards, the scrollback was improved (by me) to give the
small enhancement that *all* the VRAM not in use by the current
screen is available for scrollback: so the number of lines of
scrollback should remain constant, or virtually so. (There are
complications when the screen position is very near one end of
VRAM.)
Hope this helps
/ o Simon Tatham E-mail to: sgt20@cam.ac.uk
\ I /\/\ O /\/ http://callisto.girton.cam.ac.uk/users/sgt20
/ ~~~~~~~~~~~~~~~~~ Trinity College, Cambridge, CB2 1TQ, England