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From: greg@ccwf.cc.utexas.edu (Greg Harp)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Blitter vs. 040 (was: Computer Architecture question
Message-ID: <48817@ut-emx.uucp>
Date: 11 May 91 07:20:10 GMT
References: <1991May9.070349.15151@neon.Stanford.EDU> <3496.tnews@templar.actrix.gen.nz> <vbcH!4p@cs.psu.edu> <1991May10.180908.29565@convex.com> <6o6Hk!=@cs.psu.edu>
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Reply-To: greg@ccwf.cc.utexas.edu (Greg Harp)
Organization: The University of Texas at Austin
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In article <6o6Hk!=@cs.psu.edu> melling@cs.psu.edu (Michael D Mellinger) writes:
>
>In article <1991May10.180908.29565@convex.com> swarren@convex.com (Steve Warren) writes:
>
>   What is the avg. available bandwidth from the NeXT '040 directly into display
>   memory?  The performance of the CPU chip is not as important as the
>   availability of the display memory bus to the CPU.
>
>The 040 is equal to at least 3 68030's.  One would think that decent
>animation could be done on the NeXT.  It might just be a matter of
>being able to interrupt the OS on a regular enough basis to get smooth
>animation, which might be a problem at the current time because the
>Mach kernal cannnot be interrupted.

Well, we all know the 040 can do it.  In fact, Steve said (and I of course
deleted it before I thought I might refer to it (: ) that he wasn't
interested in how much the 040 can do, but what can be done on the NeXT
with its architecture and OS.

If Mach can't be interrupted directly that could be a problem.  However,
with nothing else really running on the machine you should be able to get
the CPU time to do a decent job.

>Does anyone know the bandwidth from the NeXT 040 to memory?

That's the question Steve asked, I believe.  I'm wondering the same thing
myself.  Also, would you have to do anything "funny" to directly access the
display memory?  You know, Mach/BSD might have something to say about
a program hitting the memory in a place not assigned to it.  

Also, hitting the hardware directly kills all that nice device
independance, you know. :)  (I _had_ to say it...)

Greg
-- 
       Greg Harp       |"I was there to match my intellect on national TV,
                       | against a plumber and an architect, both with a PhD."
greg@ccwf.cc.utexas.edu|            -- "I Lost on Jeopardy," Weird Al Yankovic