From: cse_stu@memstvx1.memst.edu
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Comdex/Quicktime released for the PC
Date: 17 Dec 92 16:54:33 GMT
Organization: Memphis State University

>> 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 video is slower than main memory. This burst thing of 40 MB/sec is what the
bus might be able to do in a space but not on earth. If everything in the
machine is shut of a program could move about 30 MB/sec but that is without
compression and without the operating system being up and that is provided that
the video ram is zero wait state which for a 33mhz 040' is something in the
range of 40ns ram or maybe lower.
> 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'.
The last data I heard on the 4000 was that in burst mode the ram does run zero
wait state and since some of the amiga anim. programs do turn off the operating
system it is possible to move some data. The other face is that the Quardra has
a 10mhz nubus with a 20mhz burst mode while the 4000's bus is capable of 100mhz
plus speed provided you have a CPU that is fast enough. You could say they are
leaving room for expansion where the mac is trying to stay compatable and
behind the times in bus design. Look at the Next its bus is like the mac and
they run it at 25mhz without any kind of burst.
>> 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?
It is the only card out for the mac that has video quailty. The encoders and
other adapters that convert standard Mac rgb will cost you $3000+ for an
encoder with enough quailty and I have not seen a genlock for rgb output that 
will let you have graphics over video that has anything more then VHS quality
video. They might tell you they can make one for $1000 or less but it takes the
video in a changes it into 230 res at best. Ads lie a lot.
One more point if you can do all these neat things what programs are you using?
=======
video man
Newsgroups: comp.sys.amiga.advocacy,comp.sys.amiga.misc