Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!sunic!cs.umu.se!dvljrt
From: dvljrt@cs.umu.se (Joakim Rosqvist)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Copper/Dynamic mode questions
Message-ID: <1991Apr24.201600.22575@cs.umu.se>
Date: 24 Apr 91 20:16:00 GMT
References: <1991Apr22.101552.47507@cc.usu.edu>
Sender: news@cs.umu.se (News Administrator)
Organization: Dep. of Info.Proc, Umea Univ., Sweden
Lines: 23

In article <1991Apr22.101552.47507@cc.usu.edu> slmvk@cc.usu.edu writes:
>
>	I have some questions on the dynamic hires/ham modes:
>
>	1.  If I understand correctly, DHR uses a standard HiRes (640 width)
>screen, but changes the palette eveney line to give more colors.  My question:
>why change the palette only once per line?  I've seen demos that change
>palettes every eight pixels (hires copper resolution sucks!), so why can't DHR? 
>					Jon Taylor

Colors can not be changed while the picture is being drawn because DHR
uses 4-bitplane HIRES. That display mode requiers *every single* memory
access. Since the display has priority over the copper the copper will have
to wait until the HBLANK. Even there the timing is tough. In normal 640-mode
the HBLANK interval is just enough for a wait and 16 colormoves but to
be able to use DHR in overscan the 68000 will have to do some of the colors
too. Sadly enough I think the 'DFF-bus' is 100% busy too, otherwise the
68000 could change some colors in the middle of a scanline when ran from
fastram.
In dynamic HAM though, the copper could change a palette value every 16
pixels so that mode could theoretically be improved.

/$DR.HEX$