Newsgroups: comp.arch
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Self-modifying code (and bitblt)
Message-ID: <1988Jul26.022555.28494@utzoo.uucp>
Organization: U of Toronto Zoology
References: <7439@ico.ISC.COM> <4894@killer.DALLAS.TX.US>
Date: Tue, 26 Jul 88 02:25:55 GMT

In article <4894@killer.DALLAS.TX.US> elg@killer.UUCP writes:
>... In addition, the blitter takes advantage of
>the fact that the 68000 only uses half the available memory bandwidth...

I.e., that the memory system is too fast for the processor to use fully.
Can you say "imbalanced system"?

>However, I still would not want to use a plain old 68000 machine which
>had to use a software loop to scroll a 32K bitmap.... I've seen Macs
>and ST's... the speed of window management and scrolling simply cannot 
>compare...

Have you tried a Blit (aka 5620, aka 630)?  That's a demonstration of
what *can* be done with a plain old 68000 using software BitBlt.  I said
Commodore didn't know how to write a fast software implementation; I
didn't mean to imply that Atari or Apple did better!  One *can* do faster
BitBlt than the Blit does, given enough added hardware, but I really doubt
the cost-effectiveness.  (Remembering, again, that the alternative is not
to leave out the custom goodies, but to use that investment of money and
hardware effort to make the CPU run faster.)
-- 
MSDOS is not dead, it just     |     Henry Spencer at U of Toronto Zoology
smells that way.               | uunet!mnetor!utzoo!henry henry@zoo.toronto.edu