Date   : Wed, 07 Dec 1994 11:34:50 +0000
From   : lamcw <lamcw@...>
Subject: Re: BBC screen emulation

Dave Barnett wrote:

;It is not surprising that screen emulation is time consuming.  What is
;needed is a scheme to optimize the emulation while being as faithful as
;possible.


The way the beeb screen is bit mapped is also horrible. I haven't come
across any games which modify the CTRC registers in a video interrupt,
they seem to modify the ULA video registers instead to change colours,
modes etc.

my graphics routine has 3 stages:-

 a) process beeb vram into pixel map (for Mac)
 
 b) this pixel map holds LOGICAL colours. convert to their PHYSICAL colours

 c) call the Mac OS routine to draw the pixel map.


Stage c) is the time-eater but there's not much that can be done about that.


Chris Lam.