Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!rpi!uupsi!grebyn!ckp
From: ckp@grebyn.com (Checkpoint Technologies)
Newsgroups: comp.sys.amiga
Subject: Re: UNIX sys V4.0
Message-ID: <22929@grebyn.com>
Date: 31 Oct 90 05:03:03 GMT
References: <9010025@hpfcso.HP.COM> <15404@cbmvax.commodore.com> <16001@hydra.gatech.EDU> <15464@cbmvax.commodore.com> <22912@grebyn.com> <16102@hydra.gatech.EDU>
Reply-To: ckp@grebyn.UUCP (Checkpoint Technologies)
Organization: Grebyn Timesharing, Vienna, VA, USA
Lines: 50

In article <16102@hydra.gatech.EDU> ken@dali.gatech.edu (Ken Seefried iii) writes:
>In article <22912@grebyn.com> ckp@grebyn.UUCP (Checkpoint Technologies) writes:
>>
>>But the 030 plus the blitter is able to do bitblits plus run
>>applications faster than the 030 alone. This is the reason to
>>have a graphics co-processor, so that your applications get more CPU
>>because the CPU is spending fewer cycles doing graphics.
>
>This is, of course, absolutely wrong (though it is a common
>fallacy).

I would be inclined to think that "absolutely wrong" means that it is
never true under any circumstances, which I don't think you meant.
I assume therefore you mean that in some cases of CPU plus graphics
coprocessor, the overhead involved with communication and other factors
outweigh the advantage of the co-processor.  This I can believe.
However, I'm indicating a very specific case, where the system parameters
are well known: a 68030-equipped Amiga (A2500 or A3000, where the 68030
in the A3000 would be faster) and the Amiga blitter. (You indicated that
you aren't familiar with the Amiga and it's blitter.)

Yes, there is setup time burdening the CPU.  I suppose I must leave it
for other, more experienced graphics guru's to indicate
whether the 68030 is better off alone, but I still doubt it.

Remember also that I'm thinking about application performance.  I have
heard many say that the 68030 *can* draw faster than the blitter
in some cases (sometimes the 68K can outrun the blitter). I'm willing to
have my graphics run a little slower to make my applications compute a
little faster.  I gain in total system throughput. This another benefit
of multi-tasking to a single user.  And I have an idea what kind of
performance I should expect, I'm using a blitter-driven Amiga now.

>>Now if you tell me that the 030 alone *can* run applications and do
>>graphics faster than the 030 plus the blitter, well then I won't believe
>>you...
>
>Never good to make statements like that when totally lacking hard
>evidence...

Ah, but what I said was absolutely true, and I have all the evidence I
need.  I really would disbelieve it, given my current understanding the
of the Amiga's graphics architecture and the 68030 CPU; this is all the
claim I was making. I need no further evidence for this than my own
opinions. :-)
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