[Coco] hardware scrolling

[Simon Jonassen]

well now... 
 
after countless experiments and headaches, hardware scrolling of a 6K hires
bitmap via $ff22 and some raster trickery is entirely possible on a coco II
!!!!

so the vdg isn't entirely dead afterall... she's hiding more tricks yet....
 
http://roust-it.dk/coco/realvsp.mpe
 
above link is a video of a real coco II and my laptop with Xroar scrolling
the 6k bitmap in hardware... 
 
the routine is only updating every 6th frame, so it can be much faster....
it can also be made to scroll further with a few more lines of code....
 
 
/Simon :-)