Path: utzoo!attcan!uunet!super!udel!rochester!cornell!mailrus!ncar!ames!oliveb!amiga!boing!dale
From: dale@boing.UUCP (Dale Luck)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Unsupported Programming Practices
Message-ID: <595@boing.UUCP>
Date: 17 Jan 89 19:20:23 GMT
References: <8901060406.AA22607@postgres.Berkeley.EDU> <84277@sun.uucp> <13389@cup.portal.com> <3669@tekig5.PEN.TEK.COM>
Reply-To: dale@boing.UUCP (Dale Luck)
Organization: Boing, Milpitas, Ca.
Lines: 44

In article  wayneck@tekig5.PEN.TEK.COM (Wayne Knapp) writes:
>          MyBlitRoutine( ...)
>          { 
>               OwnBlitter();
>               Compute blitter register values  /* let Blitter still run */ 
>               WaitBlit();
>               set blitter registers.
>               DisownBlitter();
>          }
>                                       Wayne Knapp 

In general we try to minimize the time we Own the Blitter, it is a
scarce but often used resource.
Nearly all the amiga graphics routines do something similar to this.

{
	Compute blitter register values
	OwnBlitter
	WaitBlit
	set blitter registers
	DisownBlitter
}
In a multiplane blit we use:
{
	Computer blitter registers that do not change between planes
		such as modulos, blitsize, bltconx's, fw/lwmask, etc.
	OwnBlitter
	WaitBlit
	load non changing blit registers
	for each plane to blit
		compute new changing blit registers such as ptrs to
			bitplanes
		WaitBlit
		load registers that need to be reloaded per blit.
		zap bltsize (starts the blit)
	endforeach
	DisownBlitter
}



-- 
Dale Luck     GfxBase/Boing, Inc.
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