Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!cs.utexas.edu!uunet!zephyr.ens.tek.com!tekig5!wayneck
From: wayneck@tekig5.PEN.TEK.COM (Wayne Knapp)
Newsgroups: comp.sys.amiga
Subject: Re: Denise/Paula/Agnus/Gary/Portia
Message-ID: <4705@tekig5.PEN.TEK.COM>
Date: 21 Aug 89 18:44:10 GMT
References: <1388@bnr-fos.UUCP> <713@neptune.UUCP> <522@tardis.Tymnet.COM>
Distribution: comp.sys.amiga
Organization: Tektronix Inc., Beaverton, Or.
Lines: 30

In article <522@tardis.Tymnet.COM>, jms@tardis.Tymnet.COM (Joe Smith) writes:
: In article <SHADOW.89Aug18060254@pawl.rpi.edu> shadow@pawl.rpi.edu (Deven T. Corzine) writes:
: 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.


Except that that blitter is just way too slow to do smooth scrolling,
except for maybe low-res 4 bitplane stuff.  High-res 4 bitplane, 
requires over 100ms even just to clear the memory, a simple one
source blit. 
                                    Wayne Knapp