From: Dale_Adams@gateway.qm.apple.com (Dale Adams)
Subject: Re: Comdex/Quicktime released for the PC
Date: Tue, 15 Dec 1992 22:47:08 GMT
Organization: Apple Computer Inc.

In article <1992Dec15.122849.4621@memstvx1.memst.edu> 
cse_stu@memstvx1.memst.edu writes:
> I was talking worst case and it does happen. If you average frame is 25k 
> but you have two or three frames that are 200k or so then you are going to 
> get a glitch in the animation. If your Quadra will handle that then I'll 
> believe you are talking the truth.

But all that's really necessary is to run is 25-30 fps for a smooth 
animation.  If I can normally do well over 90 (depending, of course, on 
the source material), then I should be able to handle the odd frame or two 
which requires substantially more than that.

> The 040 chip can take in 16byte's in fives clock cycles and then it 
>takes a least five clock cycles to put it back to memeory But the cache does 
> not help you and the mac bus is lucky if it can push 20mhz to memory and 
> 10mhz to it's video board.

Sorry, but this is completely wrong regarding the Quadra bus data transfer 
rates.  The system bus on a Q950 is capable of much higher data transfer 
rates than that.   And I believe you're a bit confused - you must be 
thinking of a NuBus video card.  You really don't know much about the
Quadra hardware, do you?  The Quadras have frame buffer VRAM which sits
directly on the 040 bus and has access times that are actually better 
than main memory for sustained write bursts (such as you get in 
animation).  As I stated in my previous post, the frame buffer VRAM can 
sustain data transfer rates of well over 40 MB/sec. using burst cycles.  
Now, whether the '040 can supply data at that rate is another question.  
Typically, the '040 never even does TA/TS pairs on back-to-back clock 
cycles - that's why the bursts help so much.

> The mac was not designed for speed. You can see this by looking at
> an Amiga 3000 running AMax that allows the Amiga to emulate a Mac. The 
> 3000 out runs a mac at the same speed because they have zero wait state 
> memory with burst mode on and the mac has one or two wait states. 

There seem to be a few problems here if you're trying to tell me how fast 
my Quadra runs:  AMax only emulates a MacPlus;  the A3000 has a 68030 
processor, not an 040;  the A3000 can't emulate a Quadra under AMax.  Not 
every Macintosh has the same hardware design.  Don't assume there's much 
similarity in the hardware design between a 68030 based Mac and the 
Quadras.  It was stated by a Commodore employee (on another Amiga group, 
the hardware one I think) that the A4000 (let's compare 040 machines to 
040 machines) has 5/2/2/2 read burst timing from RAM.  This is hardly zero 
wait state - it's more like 3 wait states on the first read access of the 
burst and 1 wait state on each successive access.  To be fair, using 80 ns 
DRAM, this is pretty close to the best you're going to do with an 040 
design.  A really good interleaved memory design might be able to do 
4/1/1/1 bursts (at best) with 80 ns DRAM.  Using your criteria, it looks 
like the A4000 'was not designed for speed'.

> I'm not sure because  Apple does not reveal how the hardware works.

No, you're definitely not.

> The only board that I have heard that is fast enough for animation is 
> the targa card which is real expensive and it runs on the bus that is 10mhz.

Now wait a minute.  Why is the 10 MHz bus fast enough for animation now, 
but it wasn't earlier in your post?

> Your right seeing is believing.

Yes, my seeing is right.  It's your believing (or lack thereof) that's not.

- Dale Adams
Newsgroups: comp.sys.amiga.advocacy