brianm@sco.COM (Brian Moffet) (08/04/89)
Disclaimer, I know just enough about hardware to be dangerous. :-)
I was thinking a while about my amiga 1000 last night, and considering
what kind of machine would replace it at some point in time.
I came to the conclusion that one major feature I would look for
is the ability to use more bitplanes (more colors).
I was thinking that the resolution in the 640x400 interlace mode is not
all that bad, and with anti-aliasing, it is quite reasonable. However,
anti-aliasing uses colors to do it's work. What would be the problem
with an Amiga Computer which went all out in the Desktop Video market
by providing the same resolution the ami now does, but is able to
use 12 to 24 bitplanes for color. The interlace is still there for
television, only now you can put up enough colors to make the picture
look damn near television quality.
Problems? Well, in order to do this we would need to be able to
access all bitplanes in a refresh cycle of 30 Hz for interlace, 60
for non-interlace. That is a large chunk of memory to access.
The bus between the video hardware and the memory would probably
have to be bumped in speed. The memory might have to also. However,
we would still be able to use the analog monitors that are common out
there in the amiga market, and there would be a significant improvement
in the quality/usefulness of the Amiga Desktop Video arena. the Really
Obese Agnus would be required of course :-}
What do people think? I believe this would help the Amiga further
entrench itself into the Desktop video market, and give people like
me who want to do just normal graphics more colors to play with.
brian moffet
--
Brian Moffet {uunet,decvax!microsoft,ucscc}!sco!brianm
-or- ...sco!alar!brian
"I was everything you wanted me to be. You were afraid, I was frightening."
My fish and company have policies. I have opinions.cmcmanis%pepper@Sun.COM (Chuck McManis) (08/05/89)
In regards to Brian Moffet's article wrt to more colors...
I've done a couple of video tutorials before, but I'll do just the
numbers for more colors this time...
The unasked question is, "What is acceptable graphics resolution?"
And the general answer seems to be "As good as current TV." And in
fact that is most likely true. You then might ask "How good is TV?"
And come up with a somewhat more obscure answer.
Brian was looking to get 24 bitplanes for (sometimes called "true color")
his images. I used to work at the Image Processing Institute at USC and
one of the research projects that was done there was digital compression
of video images for television. One of the results was that for most of
the people a 5 bit triple (R,G,B, 32,768 colors) was indistinguishable
from an 8 bit triple (16M colors). With that in mind you might consider
another way in which the basic amiga architecture could be rewacked.
Continue to use color registers, but keep them 16 bits wide, 5 bits each
of R, G, and B, plus on "transparent" bit for genlocking and such.
As far as memory accesses go though, if you wanted to enable a 16 bitplane
image (direct through the color DACs) that was 702 X 440 for NTSC overscan
then you are looking at 38,610 bytes per bitplane or 579,150 bytes for
a 15 bit screen, 617,760 for a picture with genlock bits in it.
With 16 bits/pixel and 702 pixels per line, you need to fetch 1404 bytes
per scanline. Using a bitplane architecture might make this a bit tougher
but the bandwidth is the same. A scan line takes just 63.5 microseconds
or about 22,110,230 bytes/second to keep the video pipeline full. Of course
ideally you would like some time for the processor to get in there as well
so you might actually want to be able to suck data out of that memory at
44,220,470 bytes/second (1 CPU, 1 Video cycle interleaved). Now on byte
accesses that would mean you need to fetch data in 23 nanoseconds, if
you had 16 bit wide memory that could be pumped up to 46 nanoseconds.
32 bit wide memory could let that slide to 92 nS. Now this also means
that your processor will need to get in and out in 92 nS, which I believe
a 33Mhz 68030 can do. Plus there are static rams available to do 92 ns
accesses on a regular basis so that's no problem.
So what is the big deal? Actually nothing at all. That is the nice thing
about engineering, you can just crank the numbers through and then go
down to Fry's electronics and buy the parts. The only hitch is that the
cost of 90 nanosecond static rams, say a meg worth at least since each
screen will take 579K bytes, hmmm maybe you better make that 2 meg (the
address space is set aside for it). Will be about $50/chip and each
chip is 32K X 8 (Toshiba TC55328) so 2 Meg will be about $3,200 your
cost, say $7,000 will be contributed to the final system price. And that
is just for the Chip RAM!
I know, there are cheaper ways to do it, look at Targa boards etc. And
the only problem is that these systems don't have the "instant update"
type effect you've come to associate with an Amiga. Even the Sun 3/80
with an 8 bit color option doesn't look "quick" until you plug in the
graphics accellerator.
The point that I've spent way to long making is that there is absolutely
no technical reason why any of the systems that any of a number of people
have fantisized about on the net can't be built. There are however monetary
constraints in that the implied assumption is "and I want it to cost the
same price as my original Amiga." which is currently impossible. I guess
this is sort of a flame too in that if it is possible I'd rather see
more stuff that said "Here is where I'd like to see the Amiga move toward,
and here are concrete suggestions for moving the architecture forward so
that 5 yrs from now when you can build it the software still works." or
"This is what I'd like to see in a high end Amiga and this is what I'd
like to pay for it." Rather than, "Why don't you guys open your eyes and
realize that a 2 billion color display would sell zillions of Amigas."
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.
"A most excellent barbarian ... Genghis Kahn!"nigel@ultima.cs.uts.oz (Nigel Pearson) (08/08/89)
in article <3128@scolex.sco.COM>, brianm@sco.COM (Brian Moffet) says: > > Disclaimer, I know just enough about hardware to be dangerous. :-) > Me too! > What would be the problem with an Amiga Computer which went all out > in the Desktop Video market by providing the same resolution the > ami now does, but is able to use 12 to 24 bitplanes for color. Main problem is graphics memory access, as you identified. But, this really is quite feasible. The way I would do it would be to treble the width of the graphics [data] bus(s). That way, you effectively treble the speed without having to muck around too much with the ami's complex timing. You could even hack up a cheap one using three sets of custom chips, with just a different D-A at the end to combine the outputs (and different colour map address', processor interface address', etc). Anyone interested in doing some work with me on this? What I would also like to see is a more sophisticated Genlock system. The main problem I perceive with the Amiga's current one is that computer generated pixels are either on or off. ie. there is no way to fade overlayed images on top of video images. How about 32 bitplanes of information, 24 for colour, and 8 for 'transparency'. This would allow computer images to have fuzzy edges when overlayed over video. Should alleviate the age-old problem of contrast induced interlace flicker. (Which, BTW, is present in almost all of the video titling hardware available today. Fix this, and you create a new market for the Amiga.) I'm all in favor of helping the Amiga further intrench itself in ANY market, but particularly in Desktop Video; where it can really 'show its true colours'. As I said earlier, I am interested in implementing these ideas (and others). Drop me a line if you have ideas/money/criticism. Cheers - Nigel. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Nigel Pearson, overpaid research assistant @ University of Technology, Sydney. "Do you want to live for ever?" - Conan the Barbarian & Highlander. ACSnet: nigel@ultima.cs.uts.oz Surface: c/o- Key Centre, UTS, PO Box 123, (Well, at least for this week) :-) BROADWAY, NSW, Australia, 2007 ________________________________________________________________________________