Re: Scrolling HGR Screen Up 8 Lines

[dempson@actrix.gen.nz (David Empson)]

Matt Ackeret <mattack@vax.area.com> wrote:

> In article <1e7m1xy.1xt42n21usiwsgN%dempson@actrix.gen.nz>,
> David Empson <dempson@actrix.gen.nz> wrote:
> >This is rather messy.  It will also look strange, with striped effects
> >during the move.
> 
> The striped one will be a lot faster than the ripple one, right?

I don't think it would be a lot faster.  It would be somewhat faster.

The only advantage of the striped method is that it doesn't have the
overhead of calculating the address of the next line.  On the other
hand, it can't avoid copying most of the screen hole bytes, which means
it copies an extra 48 * 8 = 384 bytes (assuming you avoid copying the
screen holes for the 16 lines which have to be handled specially).

My routine could be improved somewhat by unrolling the loops, paying
more attention to the relationship between the source and destination
addresses and/or using table lookup.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand