Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!apple!oliveb!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga
Subject: Re: Denise/Paula/Agnus/Gary/Portia
Summary: No need to use the copper
Message-ID: <522@tardis.Tymnet.COM>
Date: 19 Aug 89 21:49:22 GMT
References: <1388@bnr-fos.UUCP> <713@neptune.UUCP> <8566@batcomputer.tn.cornell.edu> <3036@bucsb.UUCP> <15769@watdragon.waterloo.edu> <506@tardis.Tymnet.COM> <13167@well.UUCP> <SHADOW.89Aug18060254@pawl.rpi.edu>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Distribution: comp.sys.amiga
Organization: McDonnell Douglas Field Service Co, San Jose CA
Lines: 31

In article <SHADOW.89Aug18060254@pawl.rpi.edu> shadow@pawl.rpi.edu (Deven T. Corzine) writes:
>The proposed scheme was to make one large bitplane (as far as the
>blitter is concerned) and manipulating the Copper to display the
>bitplanes, resetting the address for each line.

Actually, my idea doesn't need to bother the Copper at all.  Just set BPL1MOD
and BPL2MOD (registers 108 and 10A).

>         <---------- layout in memory --------->
>        +---------+---------+---------+---------+
>        |         |         |         |         |
>        |         |         |         |         |
>        +---------+---------+---------+---------+
>         <--bp0--> <--bp1--> <--bp2--> <--bp3-->

That's a good diagram.  The Blitter can handle this format if BLT[A-D]MOD
are set (registers 060 thru 066).  Again, no Copper hacking is required.

>Now, to scroll, the blitter is told to scroll a region starting at addr,
>len*3 bytes wide and y lines long vertically by the height of a line
>of text.  It doesn't matter to the blitter that the region is not
>displayed as a single bitplane.

Right.  The only problem, as I mentioned, is that the current Agnus has
a limitation of 1024 bits for the total width.  However the new 1-meg
Agnus is supposed to respond to requests for 32K bit wide blits.
-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
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