Path: utzoo!attcan!uunet!jarthur!usc!cs.utexas.edu!rutgers!cbmvax!jesup
From: jesup@cbmvax.commodore.com (Randell Jesup)
Newsgroups: comp.sys.amiga.tech
Subject: Re: How fast is the BltBitMap() routine?  (Anim. speed & redraw)
Message-ID: <14699@cbmvax.commodore.com>
Date: 27 Sep 90 20:04:54 GMT
References: <11825@uservx.afwl.af.mil> <1437@metaphor.Metaphor.COM>
Reply-To: jesup@cbmvax.commodore.com (Randell Jesup)
Organization: Commodore, West Chester, PA
Lines: 31

In article <1437@metaphor.Metaphor.COM> djh@neuromancer.metaphor.com (Dallas J. Hodgson) writes:
>In article <11825@uservx.afwl.af.mil> GALETTI@uservx.afwl.af.mil writes:
>>How fast is the graphics.lib "BltBitMap()" routine?  It seems to me that
>>setting up the blitter for a copy shouldn't take all that much time. 
...
>>I am using BltBitMap() to do the copies.  For those of you who have experience
>>writing your own blitter routines, do you think it would it be worth my while 
>>to write a replacement for BltBitMap()?  How significant would the speedup be?
...
>What timing, I was just experimenting with this last night. For the
>animation I was working on, I tried this two ways: Using BltBitMap, and
>using a near-equivalent routine which had CopyMemQuick at its core. The
>CopyMemQuick routine was always significantly faster, even with FAST RAM and
>caching turned off on my A-3000.

	You can improve on the speed of BltBitMap for special cases, and
if you can avoid other special cases.  For example, BltBitMap would normally
only need a source and destination for a straight copy, except that for
some types of alignment of source and dest the masks aren't sufficient, and
a second source channel (A) is needed to point to a small mask in memory.
An '030 may be able to keep up with the blitter on nicely aligned copies
(such as scrolls), though of course it can't be doing anything else in the
meantime.

>This may not hold true for 16-bit Amigas. I plan to do an A-1000 benchmark
>tonight.

-- 
Randell Jesup, Keeper of AmigaDos, Commodore Engineering.
{uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.cbm.commodore.com  BIX: rjesup  
Common phrase heard at Amiga Devcon '89: "It's in there!"