From: lindblad@klaava.Helsinki.FI (Jarkko Lindblad)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: A4000 at WOC
Date: 28 Sep 92 19:08:57 GMT
Organization: University of Helsinki

wallmann@backus.pu.informatik.th-darmstadt.de (Natuerlich!) writes:
: In article <1992Sep25.175523.20771@klaava.Helsinki.FI> lindblad@klaava.Helsinki.FI (Jarkko Lindblad) writes:

: >	There was a review on some magazine many years (it was
: >probably 1985 or 1986) (can't remember what magazine it was) ago,
: >which said this.
: Well it was wrong.

And you as an a die hard Atari ST owner from 1985 are right?

: >: about but giving what you guess away as facts.
: >
: >Well, Dave Haynie said that it is/was roughly 25 to 50% of the speed of
: >Amiga blitter. Somehow I usually trust him...
: That's why you buy Amigas (har). I don't have both machines, I just have
: the two reference manuals. Just from the paper I'd say the 25% to 50% would
: be best case, when you are mixing three sources into one destination. Which
: the Atari blitter can only do successively.

Also Atari blitter trashes two of the three sources in this process.
And there is only your word that says that Atari's blitter uses the
whole bandwidth available in simple operations.

: For your 'normal' operation scrolling windows and the like, the speed of
: both is limited by the buswidth, which in comparison between the A1000 and
: the ST is really the same. Now taking into consideration that the ST runs

Are they? And what's the speed of ST's bus?

: 10% faster anyhow... Somewhere someone oughta have made some tests
: giving some figures about pixel blit rate per second, of both blitters
: this would be a lot more informative than guessing (guilty!).

Ah, so when I do a guess, I'm clueless (as you will say later), but
when you guess you're not. How nice. Perhaps you should copy some of
the most important pieces of information on the ST bus and blitter
from the manual you claim to have.

: >: The truth is: the Blitter does DMA it does share the bus with the
: > [ stuff deleted]>
: >: CPU and can blit concurrently. TOS in its singletasking incarnation didn't
: >
: >Hmm, everyone else say it does not do anything concurrently with CPU -
: >and I also may easily say that - however even if it did, it'd had to
: Everyone else in your case are Amigoids who think on the level "what
: must not be, can not be". The hardware design is like this if both
: want to access the bus, 50% go to the blitter and 50% to the CPU 
: (ignoring disk DMA for now).

Okay - I should have said "at the same time at full speed" - I assumed
this. Of course it's possible for the two pieces to run concurrently
reven on the same bus (even Amiga can do this if needed).

: >share the same bus with CPU and therefor neither of the ones could
: >operate at full speed. Blitteri that is slower than CPU is not
: >practical in single bus systems like Atari ST, Falcon and Commodore 64.
: And AMIGA 1000 you forgot...

1. 68000 is definately not faster than blitter. It can do some small
operations faster because blitter needs some setting up, but for 99%
of operation blitter outperforms 68000 by huge margin.

2. Amiga 1000 is not a single bus design.

: >: make use of this, I am curious whether they will use this in MTOS.
: >
: >I guess the next thing you will say about me is that I lie when I say
: >that neither the CPu or the blitter can operate at full speed
: >concurrently if they share the same bus.
: I'd only do this if I was as clueless as you...

Thank you for flaming. Perhaps I should reopen my kill-file once more.

--
Jarkko Lindblad
lindblad@cc.helsinki.fi