Atari v Commodore

[frogstar_robot]

I would go with Atari here, on a personal/technical basis. You can't, AFIK, hook up a C64 to a TV set; certainly not with AV cables. And that's where I'd want to play it. Also, there are tons of cartridge-based games for Atari computers; I don't think there are as many with the C64.

 

Yes you can. There is a DIN connector on the back that supplies composite and separate luma/chroma. With the appropriate cable it can be connected to either composite inputs or "s-vhs" connectors.

 

Actually this is one area where a C64 will often give a better out of the box experience. Atari made some boneheaded decisions on the analog video circuitry on many models up to and including leaving separate luma/chroma disconnected. It is common to modify A8s for better video output.

[Wolfram]

I would go with Atari here, on a personal/technical basis. You can't, AFIK, hook up a C64 to a TV set; certainly not with AV cables. And that's where I'd want to play it. Also, there are tons of cartridge-based games for Atari computers; I don't think there are as many with the C64.

 

Now Amigas, you can hook up to a TV. But, again, most of the games are disk-based, and are hard to find in NTSC format-as are Amigas themselves.

 

 

you can hook up a c64 to a TV set. it was designed to be connected to TVs from the very start. AV cables, no problem. but AFAIK a8 has no AV (composite) out built in. I might be as wrong as you were with TV sets tho.

 

cartridge based games got outdated in the early 80s. they suck anyway to disk based ones, regarding c64 games.

[Fröhn]

To be clear, on a composite, baseband video display, C64 has interlaced color. A full image occurs every 1/30 second. On a separate chroma / luma display, a full image occurs every 1/60 second.

Composite or Y/C has nothing to do with the refresh rate or interlace. It's always 60 Hz.

 

Monochrome pixels are the same either way. Because the C64 has seperate chroma, it's accurate to say it does 320x200x16 @ 60Hz, and I didn't mean to imply otherwise. To see it, one does need to use a good display.

PAL/NTSC doesn't know the concept of "pixels", only the computers (A8, C64 etc) do. The monitor will smoothly fade from one color tone to another and needs approx. 4-6 hires pixels to do so. Luma is much more accurate so you can still see each pixel but with fading color tones (that's the weird borders which are visible when you have a color tone surrounded by a different one).

 

When doing the PAL color tricks, it takes a 1/25 sec to obtain a full color image, on EITHER MACHINE.

The 50:50 one-line-to-the-next mixing works in 50 Hz / 60 Hz and does NOT flicker at all.

 

Neither machine does any real horizontal interlace.

C64 does in that 160x200 mode.

 

There is pixel shifting for some overlap and additional detail

That's exactly what "interlace" is: 0.5 pixel shifting every 2nd frame to simulate a higher resolution.

 

Vertical interlace appears possible on Atari machines. I've not seen this on VIC II on a C64.

Vertical interlace is not possible on C64, but horizontal interlace is.

[emkay]

Atari density colors

 

vs

 

 

Simple, but more density

 

and more much

 

Color depth is usually measured rather than density and that favors Atari on GTIA modes and gprior enhanced modes.

 

Yes. C64 graphics suffer heavily by the "depth" as regular systems did. The Atari can display depth and/or colours.

[emkay]

I really should find the time for making other examples.... Those C64 blindflyers make me nervous...

 

Well this unfinished picture show 48 real colours per scanline... no interlace is used. Whre is anyhow anything compareable on the C64? 80 colour per scanline were also no problem.

[emkay]

Color depth is usually measured rather than density and that favors Atari on GTIA modes and gprior enhanced modes.

The C64 can also do 80x200 @ 16 colors with complete freedom which of the 16 colors to use. But that is only a subset of the FLI mode (160x200) which has an even higher color depth.

 

Atari 80*240 256 REAL colours without interlace

 

With interlace 160x240 256 real colours

 

 

...

 

 

With interlace you can also reach the colour depth of the C64 .... easily toppping it.

[emkay]

The term 'interlaced' is often misused in graphics trickery. I think the term should only be used when refering to a real interlaced image as in 480i or 576i.

 

OK... So please put the A8 into this line with 480i !

[potatohead]

Frohn:

 

Composite will have different display qualities over Y/C, and you are confusing refresh rates with how the color actually is drawn to the screen.

 

So, let's take a full frame. One full frame is actually 1/30th of a second and is composed of two sub-frames.

 

Our home computers of the 80's skipped out on the half-scan line required to build a full, vertically interlaced frame, leaving us with 1/60 second NTSC motion capability.

 

There are two forms of interlace possible on a composite, NTSC signal. Vertical interlace, which is not the point of discussion between us, and HORIZONTAL INTERLACE, which is.

 

When a C64 is viewed through it's composite video output horizontal interlace IS present, and it's in play to achieve the 320 pixel color resolution inherent in the machine. The color alternates phase every other scan line, allowing for a shift in where the color information appears on screen. This is NTSC standard and needs to occur on a composite input, or said input will be limited to about 160 pixels of information. Truth is, you can overdrive it to about 256, which is what the TI computer does, and only experience some artifacts.

 

To get to 320, interlaced color must be used, or... separate signals must be used. On the C64, you get both choices!

 

In any case, in the composite or RF configuration, a full color image is NOT seen, until a FULL FRAME has been scanned and that takes 1/30 sec to do. This is true for your Xbox today as well, if it's running on a composite video display path. Go hook it up, and watch the dot-crawl inherent in INTERLACED color images on NTSC.

 

When a C64 is viewed through it's Y/C output NO horizontal interlace is necessary as the separate color signal is plenty to display 320 pixels of color information. A full image is then seen every 1/60th of a second, and that's exactly why they provided that kind of output in the first place. That's a very good thing, IMHO.

 

In no case does the choice of signal carrier method impact the refresh rate of the display as a whole. I never said that it did. What I did say was that somebody viewing an interlaced color display, through a composite video connection, will see detail artifacts, if the object motion exceeds 1/30 second. And that's as true for the C64 as it is an Xbox today.

 

 

As for there being no "pixels" and the color being an analog thing, you are absolutely correct. There are color cycles. There are 160 of them in the active, safe display area on an NTSC scan line. These cycles can be either NON-INTERLACED, where the phase of each scan line is the same, or INTERLACED, where it's alternating every other scan line. Your DVD player menu is a great example of the INTERLACED, as is your C64, Xbox and other devices using a composite output.

 

However, stating that for the purposes of the discussion we are having right now, does not add any value. Of course it's analog.

 

Here are the facts on that then:

 

A NON-INTERLACED composite video signal will carry 160 pixels to the display with enough quality so as to permit the viewing of them as individual, discretely colored pixels. Any combination of said pixels can be resolved well enough for the viewer to differentiate their color intent. And that is true for the 160 color cycle active display area, often referred to as the NTSC safe area.

 

If a display system exceeds that 160 pixel number, the signal being analog will smoothly degrade accordingly. At 200 pixels, it's possible to still discern most of the colors, but not all, and the pixel quality is less. At 256, there is some bleeding between pixels, with some color combination significantly impacted, etc... The only assurance is at 160 pixels. Each pixel, or combination of pixels generated, will be carried to the display with enough precision to be rendered. The viewer will always be able to discern what pixel is what, in combination or not.

 

Put simply, if one computer pixel = one color cycle, then that pixel is going to be rendered near perfectly on a composite signal, every single time.

 

THIS HAPPENS AT 160 PIXELS, per SCAN LINE. That is the native Atari resolution.

 

We don't express this in terms of hard limits most of the time. Minimums are reasonable to express, and that's what I just did. One color cycle per pixel, IS FULL RESOLUTION.

 

Because of this, the smooth blend of pixels over 5-6 pixels is bunk. An entire color wheel is contained in one color cycle, period. Shitty display devices might have that property of smearing and smudging, but the signal specification does not. I do NTSC color generation all the time. This is how it works. My better devices do not have that wierd behavior. The older and more lousy ones do.

 

Ok, so that's color.

 

 

Now, interlace in more detail. This time, let's just consider monochrome pixels.

 

Case 1.

 

OO

.OO

 

That's interlace. Some portion of the pixels overlap, but not so much. If the upper row of pixels was 320, and the lower row of pixels was 320, with a half pixel shift, then the total display would be 640 pixels, INTERLACED. All good.

 

And let's just say those are drawn on the same scan line, every other frame.

 

A full image then would be 1/30 second to be seen.

 

 

Case 2

 

Pixels are now 160 pixel mode pixels. If they are shifted by 1/2 a pixel, then they have significant overlap. Think twice as wide as the ones I wrote about above. 320 pixels of resolution is implied, but not all combination of pixels can be seen, because of the overlap. The resulting display will have some information shared between the pixels, no matter what. This is because they overlap significantly.

 

When this is done, the illusion of higher resolution is seen. However, this really isn't "interlace" in the sense of what interlace is typically referring to. It's more like interpolation than it is interlace, and the Atari shifting methods are exactly the same thing. NOT INTERLACED.

 

On Atari, this is the GTIA shifting to get 160 pixels, and on C64, shifting to get 320 pixels from multi-color modes, for example.

[FastRobPlus]

This thread is wrong starting from topic's title.

 

The original interesting question was: Does anybody have any views on where any titles were launched on both Atari and Commodore - and the Atari version is the better of the two?

 

Yeah, we kind of got overrun by trolls. In all fairness, I blame the original poster's poor choice of title.

 

I did learn a lot from this thread:

 

- fanboi threads work best when you set the filter to ignore posts form the craziest nuts, (at the expense of some humor)

 

- the c64 guys are mostly from Europe, and their insults ("You're a communist!") are so culturally irrelevant that its genuinely funny.

 

- The scene talk is annoying as hell since half the users here are from the US/Canada which does not have a demo "scene" but instead has retro gaming.

 

- A8 does appear to be the equal in most ways to the C64, and the better in many more ways. Honestly I was never a fanboi (rich enough to afford a C64, 1200XL, Vic-20, TI99/4A, Northstar Horizon as a kid) so I never paid attention to this discussion before. I'm surprised the A8 is so solid against the competition despite being older than many other 8-bits.

 

- Nothing posted earlier in the thread is ever internalized, so this thread is now infinite as new fanbois coming in with the same straw-man rants.

Edited April 17, 2009 by FastRobPlus

[potatohead]

I wish we had a scene in the US

 

It's different, but I've followed it for years. Lots of fun to be had.

[frogstar_robot]

AFAIK a8 has no AV (composite) out built in. I might be as wrong as you were with TV sets tho.

 

Most models do. The A8 has a DIN5 connector similar to the one on the C64. I didn'

t mean that the A8 doesn't have a composite output but it is true that the video output circuitry, that is the video amp and so-forth, on many models can use some improvement.

[atariksi]

I really should find the time for making other examples.... Those C64 blindflyers make me nervous...

 

Well this unfinished picture show 48 real colours per scanline... no interlace is used. Whre is anyhow anything compareable on the C64? 80 colour per scanline were also no problem.

 

Looks like replicating player #5 is an easy way to add 16 shades/colors in Graphics 9/11. It looks like the formula for Graphics 11 with player #5 on top is Color = (P<<4)|((Peek(712)|Peek(711))&0xFE) where P is the pixel value (0..15) so Color range is 0..127.

Graphics 9 is a bit better since Color = P|((Peek(712)|Peek(711))&0xFE) where P is pixel value of 0..15 so Color range is 0..255.

[atariksi]

I would go with Atari here, on a personal/technical basis. You can't, AFIK, hook up a C64 to a TV set; certainly not with AV cables. And that's where I'd want to play it. Also, there are tons of cartridge-based games for Atari computers; I don't think there are as many with the C64.

 

Yes you can. There is a DIN connector on the back that supplies composite and separate luma/chroma. With the appropriate cable it can be connected to either composite inputs or "s-vhs" connectors.

 

Actually this is one area where a C64 will often give a better out of the box experience. Atari made some boneheaded decisions on the analog video circuitry on many models up to and including leaving separate luma/chroma disconnected. It is common to modify A8s for better video output.

 

The luma signal is present on all Atari 800/XE/XLs that I have. Chroma is present on XL/XE that I have. C64 A/V plug has an audio in signal on one of the lines so it's different than Atari A/V cables.

[atariksi]

I really should find the time for making other examples.... Those C64 blindflyers make me nervous...

 

Well this unfinished picture show 48 real colours per scanline... no interlace is used. Whre is anyhow anything compareable on the C64? 80 colour per scanline were also no problem.

 

Looks like replicating player #5 is an easy way to add 16 shades/colors in Graphics 9/11. It looks like the formula for Graphics 11 with player #5 on top is Color = (P<<4)|((Peek(712)|Peek(711))&0xFE) where P is the pixel value (0..15) so Color range is 0..127.

Graphics 9 is a bit better since Color = P|((Peek(712)|Peek(711))&0xFE) where P is pixel value of 0..15 so Color range is 0..255.

Graphics 11 is 0..254 step 2 (or 0..127 in bits 1..7).

[Barnacle boy]

- the c64 guys are mostly from Europe, and their insults ("You're a communist!") are so culturally irrelevant that its genuinely funny.

No one said "You're a communist" (although an Atari fan did label Jack Tramiel a communist). Earlier, Oswald remarked that speccys were popular in communist block countries. Also, when you criticised computers built with lightweight materials, Oswald joked that you'd "adore early communist pc clones. they are fuckin big and fuckin heavy using lots of materials. customers dont want anything but computers being 10kg heavy. yeah.. ". But that was obviously a joke. It was more a dig at the buying habits in communist block countries at the time than a dig at you.

[potatohead]

"I'm surprised the A8 is so solid against the competition despite being older than many other 8-bits."

 

And that's why I kept the thing!

 

Atari 8 bit computers are great computers. Their display system is flexible, making a lot of things possible. Over time, what is possible continues to escalate. This is a great thing.

 

SIO / XIO might not be the fastest thing there is, but it is great systems engineering and programming, particularly when 8K of ROM is considered.

 

I personally really groove on the overscan and scrolling. Filling the screen, or making use of better displays over time is just sweet! Might not ever get done, but the new 16:9 displays make sense on an Atari 8bit computer. Overscan is nice because it lends that feel of a big game map in a big way. The border distracts from that, and is a minus.

 

As a kid, I had a scope and modified color TV. (used to fix those, swapping CRT's, etc..) The modified TV would display the entire NTSC frame. For the 80's this was pretty cool. The scope would show waves drawn on POKEY, and the TV showed lots of things. In the 80's mics and such would be in the non-active frame all the time. They have since cleaned most all of that up, due to newer displays having a lot less overscan.

 

Many newer TV's have a service menu. If you've a flat screen CRT, chances are you can adjust it to display all but about maybe 5 percent of the frame, without impacting your viewing. I've done that to my WEGA, and it's great. Anyway, back then it was impressive to explore the audio and visual space with the Atari. It could use those extra areas and POKEY could output a lot of stuff. (direct DAC mode, with the different channels is a sweet feature --only used it for two channels then, and that was to "dither" for better waves)

 

The I/O was good for controlling things. Had the Atari at one point sending Morse Code on my HAM radio transmitter. Used a simple BASIC program, and something from ANTIC that provided a keyboard buffer. Type in your reply, let it send and get ready to deal with theirs.

 

This will piss the C= guys off, but frankly, I would take a Color Computer 3, over the C64. If more color at better resolution is the deal, that one had 640x200x4 colors RGB, and 160x200x256 composite, NTSC artifacting. Where technical computing was concerned, it had good software OS/9, nice ports, and could be expanded easily with it's cart slot. Interestingly, it's video system fetches 160 bytes per scan line, and works on one half the clock cycle, meaning it does not impact the CPU, and it has raster interrupts both VBLANK and HBLANK. Since the CPU is a 6809, and it can clock up to nearly 2Mhz, it's got plenty of horsepower for moving objects done straight up, old school software with display buffering, or just drawing in the blanking. Your choice.

 

I've got one now, and plan to do some stuff with it.

 

I had the use of a C64 for quite some time. An uncle bought it. He had a great word processor for it, that would do conditional text assembly. He used it for sweet, parametric real estate contracts. That's kind of like how attorneys today use Word Perfect. He got a lot done on that little machine, and used it well into the 90's. I would swing by and give it some TLC, or go shopping for parts.

 

Technically, I didn't like the machine all that much. Considered it a game machine, and it's a great one! Lots of fun stuff to be appreciated. How the disk worked seemed goofy to me and still does! I think a lot of people put their computers to work. And the C64 had some good attributes to offer in this respect, and for the gamers, there was lots to do. A good friend owned a C64, up through until the end. I modified his 1541, with some copy anything add on, and I think he basically copied EVERYTHING. Played it often, and we had good experiences.

 

So, it's just not a bad machine. Let's put that on record. I sure liked it. I think it's easier to post up a game on that machine, and keeping things easy means better overall visuals with less effort. That was great for software development, but today the hard factor as well as the "what's possible" factor, make the Atari the more interesting, and I think, enduring machine. Atari set the bar and set it nice and high. I appreciate that.

 

Perhaps that's part of the fanboi (and that's funny with the "i") bit is the two are a lot alike. If somebody caught a fancy for one or the other, that's probably gonna stick. I know it did with me. These days as people age, scenes change, etc... every warm body counts! As far as I am concerned, I have time for a micro, and perhaps one or two 8 bitters. Since the Atari is there, C64 kind of is redundant, which is why the the CoCo 3. Might as well enjoy the killer CPU.

 

I'm sure others have similar life trade-offs to make.

Edited April 18, 2009 by potatohead

[Bryan]

We don't express this in terms of hard limits most of the time. Minimums are reasonable to express, and that's what I just did. One color cycle per pixel, IS FULL RESOLUTION.

 

Because of this, the smooth blend of pixels over 5-6 pixels is bunk. An entire color wheel is contained in one color cycle, period. Shitty display devices might have that property of smearing and smudging, but the signal specification does not. I do NTSC color generation all the time. This is how it works. My better devices do not have that wierd behavior. The older and more lousy ones do.

 

You may be a little confused as to the fine details of how TV's work. There are many good documents on the process and I recommend the book Video Demystified.

 

TV's do not examine the positions of things in the signal and then generate a perfect color as if from a look-up table despite the fact that it may appear this is what is happening. The television does all color generation in the frequency domain. The colorburst provides the reference signal. Every line, the TV aligns its oscillator with this short 'tone' embedded in the signal. During the line, a filter of some degree of quality extracts the 3.579MHz content from the picture (NTSC). The idea is that a color and b&w picture are the same except for this added hi-frequency content (for backwards compatibility). The color decoder is always comparing its reference frequency with the one extracted from the picture and generating a difference angle which will become the basis of the color. Any content in the b&w base image that has a frequency close to that of the color signal will degrade it and this is the basis of artifact coloring.

 

The color decoder doesn't do one comparison per cycle (which would give you a clear definition of color resolution), but rather the difference angle is always in motion and often in error unless an area of the same color exists for a couple of cycles. When certain colors are placed side-by-side, the change in angle is slight and the response is fairly quick. When the angle must shift upwards of 180 degrees, the response can be quite slow.

 

Dot crawl is simply the result of the 3.579MHz color carrier becoming a visible part of the picture during high-saturation color. A standard NTSC signal has a fractional-clock line length of 227.5 clocks so each successive line is aligned to a clock with alternate phase producing the checkerboard appearance of dot-crawl. The Atari video circuits use a non-standard 228 clocks, so there is no phase alteration from line to line. Also, the Atari's saturation is limited so the pattern is not visible on most sets although it may appear as thin vertical bars when sharpness is turned up.

 

I'm not that familiar with the 64's video, so I do not know if it uses alternating phase for the color.

 

This is not, however, the same thing as the alternating decoding phase used by PAL. With NTSC, the relationship between the color carrier and the color produced is always the same, regardless of the clock's absolute phase within a line.

[potatohead]

That's basically hysteresis. I'm aware of that and big changes stress things. Again, good quality displays will exhibit very little of this, while poor quality ones exhibit far more. Modern displays are quite fast and can be treated accordingly. We've come a long way since the TV's of the 80's.

 

And I do understand about the frequency domain bit too. What people get confused about is the frequency component of a pixel. If you plot a wave out on paper, it's period has a length right? Well, one color clock = a length on the screen equal to an Atari 160 mode pixel. It's that simple. If a pixel exists that is smaller than that, some component of it's frequency will be greater than the color reference, and will be seen as color information.

 

With computers and pixels, the size of the pixel is related to the frequencies used to describe it. The position of the pixel on the screen is simply a visual confirmation of it's phase, with respect to the reference signal. Two ways of thinking of the same thing.

 

If you make a really small pixel, it is composed of higher frequencies. Where you put it impacts the phase.

 

Everything boils down to sine waves. If you make something nice and square, like a pixel, that's not a single wave. It is the sum of a fundamental wave, plus a lot of harmonics. The smaller the pixel, the higher the set of frequencies required to describe it, right? At some point, if the pixel is small enough, the frequencies used to describe it enter the range of frequencies the display device will see as color information.

 

You said: "Any content in the b&w base image that has a frequency close to that of the color signal will degrade it and this is the basis of artifact coloring." Exactly!! And those artifacts generate colors that lie at angular displacements on the color wheel, depending on their position on the screen. That position can be translated to their phase with respect to the reference. These are the same things!

 

Artifact colors can be quite complex and create very good displays. Your Atari creates artifact colors every day of the week. It does it, when you ask for colored pixels on the screen, and this is how:

 

Let's look at the Apple ][ computer display. It applies what I just said perfectly. It's the simplest and most known case.

 

It's got monochrome pixels. No color generator at all exists in that computer. The only thing that does exist, is a phase shift bit in each high resolution screen byte, that will shift things over a small amount. You get to turn the color burst on or off, that's it.

 

On a monochrome display, the Apple ][ is a two color device. Either set or reset the pixels. Right?

 

On a color device, the Apple can produce black, white, orange, blue, cyan and magenta. Where do the colors come from?

 

They come from the fact that pixels smaller than one period of the NTSC color reference signal have frequency components that are seen as color information by an NTSC composite or RF display. So then, one can look at it in the frequency domain, or one can look at it in the pixel over time domain.

 

If the reference signal is stable, then the position of a smaller pixel determines where that pixel color will be on the color wheel. It's relative size determines if it's mostly color info, half and half, or just intensity info. (frequency components) The apple has two pixels per color clock, and each one has a distinct color, based on it's position on the screen. Even pixels are one color, odd ones are another, and two together do not produce a color, only intensity. The small shift in pixel position (or phase, if you want to think of it that way), brings two additional colors to the display.

 

This is where I learned this first. The Apple.

 

Now, let's advance the tech a bit. The Atari display has 15 hues, plus intensities. Setting aside the 320 mode for a moment, one intensity only pixel will occupy a space on the screen, equal to the distance the electron beam travels for ONE color clock. If that pixel is a color pixel, additional information is added to the signal, at a higher frequency, to tell the TV what color it is.

 

If you go ahead and connect your Atari to a monochrome display, this higher frequency information manifests as small pixels! Monochrome displays have a wider frequency range, because they don't have filters for the color detector. They display EVERYTHING. And everything appears as pixels!

 

(this is for computer graphics --fully analog color signals do not manifest as pixels, but for special high-detail cases)

 

Each Atari 160 mode pixel then will present on a monochrome screen as a smaller pixel that takes one of 16 possible positions with respect to the color beam. If you color cycle on an Atari, you can literally see this motion on the screen with a monochrome display.

 

My point being the frequency domain can be seen as pixels on the screen, and can be considered as pixels where the generating of color is, if we ignore saturation.

 

The Atari is actually quite simple. There is a counter somewhere that indexes each 160 mode pixel. When a hue is asked for, the color information is output at the right phase, according to that counter, one unique position for each hue so displayed. That's 2400 little pixels actually, if you want to think about it as pixels! And on the Atari, one of those 15 positions is output for each 160 mode pixel, and that's the hue value encoded for display.

 

|00000000000000|000000000000....

|x0000000000000|000000000...

|0x000000000000|00000000...

|00x00000000000|0000

 

In the little ASCII art I put here, the top one is a monochrome pixel, the next one is hue 1, the next hue 2, the next hue three. Think of it how you want to think of it. That is what is seen if you factor out the color info.

 

One thing I've learned is that you can set multiple little pixels for blends of color as well. The Atari does not do this, nor does the C64. The Color Computer 3 can, because it has a 640x200x4 color display. On that machine, that's 4 little pixels per 160 mode pixel, each with 4 possible intensities, for a total of 256 combination possible that all fit within one color clock.

 

Because that machine uses fixed color timing, like the Apple and Atari do, it does artifacting like the Apple and the Atari does. Pixels smaller than one color clock are seen as color info.

 

Put those combination on the screen and you get 256 colors. (actually about 225, because a few of the patterns do not make colors that are all that unique)

 

Again, this occurs because the frequency components required to describe the pixels electrically exceed those permitted for intensity only, and are picked up by the color circuts in the NTSC television.

 

In my blog here: http://www.atariage.com/forums/index.php?a...;showentry=5974

 

You can see that play out for a high color display.

 

If the video device has more pixel options, then that device can describe more color, because it offers more frequencies.

 

You can see that here: http://propeller.wikispaces.com/file/view/...07_10_03_02.jpg

 

In that screen shot, the colors running down along the bottom are the native colors generated by the device. There are 89 of them, and they are stable up to 160 pixel resolution in the safe area. The ~400 or so color pattern shown above is with a pixel clock of 320 pixels, which permits two sets of color information to be seen in one color clock, and the result is a mixture of the base colors. That's a propeller, BTW. Only some of the 89 colors were used. Truth is, with this information, the device will do well over 1000 colors. Those are the best ones however.

 

This all occurs because fast pixel clocks generate frequencies that are seen as color. I prefer to think in terms of pixels, because it makes things quite easy. Frequency / time really is the same thing as pixel size and position relative to the color reference. The TV is just a simple O-scope, in this regard.

 

BTW, the reason big changes take time is that the color wheel, rolled out as a line, has a length!

 

Ask for a blue pixel and a blue green pixel and those are closely aligned. No worries. All displays will resolve those. Ask for a red one, then a blue one, or some other combination that has a large angular displacement on the color wheel, and it's literally not possible to encode that data because of the color frequency itself! So that transition takes time. The larger the angle, the larger the time. The largest time is ONE color clock for encoding. What the display renders depends on how fast it's color circuits are, and how sensitive to harmonics it is. (harmonics are the color shadows seen on lesser displays after high contrast color and intensity transitions are seen.

 

A studio quality display will, in fact, display ANY color combination correctly, so long as it's one color clock or longer. So then, in effect, you get the whole color wheel every color clock, just like I said.

 

Final example:

 

Let's say I make a monochrome display capable of 1280 pixels in the safe area. 8 * 160. If those pixels have only two states, on and off, that display will generate 8 unique colors, if only one of the pixels were set within a given color clock. If, the states of all the pixels were addressable, then that display would render 256 colors, give or take a few, like in the case of the Color Computer. Some patterns don't differentiate enough for our eyes to see, and that's how it is. I've done this on micros, just like it was done on the Apple. Works great.

 

In the simpler case, of only one being lit, sequentially setting those pixels, would produce colors at angles 360 / 8 around the color wheel. In the more complex case, the actual color seen is a sum of the angles present.

 

We are talking about the same thing. I'm just doing it in terms of discrete pixels over time, and you are talking about it in terms of frequency over time. BTW, if you want to consider what color a display will produce, you will do the math on your pixel clock, and arrive at the same place I did. Just takes longer...

 

All of that, BTW perfectly describes why Atari colors have a fairly consistent saturation. No information of that kind is being sent to the display. It's artifact only, which is why it looks the way it does.

 

I've written code to do these things, posted up the screenies, and there it is. Most, if not all, computer color in the 80's was done this way, with many devices to this day still doing it this way.

[potatohead]

The C64 was an advance because it DID use alternating phase for it's color. That's the only way to get to 320 pixels on a composite signal path.

 

Put another way, the Propeller screenie I linked, ISN"T POSSIBLE with alternating phase color. The resolution then would be high enough to prevent artifacting from happening. That's Atari style color timing. Fixed.

 

NES was another one that did alternating phase, BTW. Genesis, 7800, and others didn't, and that's why they have the look they do.

 

BTW: Eric Ball has written a nice driver for the Propeller that generates the color signal directly from a monochrome DAC output. It looks sweet, and offers better control. These kinds of outputs didn't generally exist in the 80's. They turned the color burst on, clocked monochrome pixels at one size, and sub-clocked color ones with a faster clock to generate x number of hues, depending on just how fast that clock was. Saturation was not considered as it requires a more complex display, clocked at a higher frequency to produce.

Edited April 18, 2009 by potatohead

[+wood_jl]

In playing with the emulators, it's been interesting to try out as many Commie versions of my favorite Atari games, just to note the little differences. (Archon, etc.) I've always liked different versions of the same game. I still play Dig Dug on the 2600 when I can play the real thing on Gameboy Advance. In the torrent, (hundreds or thousands, don't know) there are too many to look at, but the games are certainly on par with the Atari; they don't "suck." Even if they're not my favorite version, they're interesting to play. Of course the pallette is down but hell, these machines are very close and the games look good, and the music is indeed good. Young whipper-snappers who live only for Xbox 360 1st person shooters would laugh equally at both machines. I guess that's why it's suprising - and entertaining - to find such lively debate.

 

Amazingly, those who come here for the sole purpose of arguement shall do it incessantly and not heed a thing. Trying to turn the debate to a more practical aspect - peripheral emulation - hardly got a squirt of piss out of the hardcore fanboys, which proves my point they're just here to argue and not reason. Considering the age, lack of availability, unreliability, and inconvenience of floppy disks, HOW COULD THIS NOT BE A MAJOR ISSUE if you want to advocate for - or against - your machine that you're a fanboy of? That's right - you're here to merely argue, and an arguement of peripheral emulation (or any other issue that REALLY MATTERED) would be decided too quickly for a chronic arguer's taste.

 

SIO2PC for Atari clearly wins, at $50 it's an end-all-be-all storage solution and also emulates all other devices. All of the affordable solutions (SIO2PC-like) on C64 are likely to NOT run many games, due to the complexity of the 1541 drive, which must be emulated, processor and all. So it's the "1541 Ultimate" that you need for a C64 and it's freakin' expensive at 110.45 Euros including shipping. That's $144!! (I ordered one so I know) It's rather like SIO2SD on Atari, but necessary to play all games on C64. It appears sophisticated, but the Atari clearly wins in the "practical use" department today, period. With a $25 Atari and a $50 SIO2PC you're golden; top that.

 

Why be a fanboy on these antiques? Gigs of free software is just a mouse click away on the pirate bay, all organized neatly into alphabetized folders. When in history have things even been like that? Why not just play free games on the system you used to hate? And if all you need is the keyboard/computer and not bulky drives and shit everywhere, a Commie 64 will fit in nicely with my rather large collection of gaming systems (although I'm running in a pretty tough crowd of collectors here, so maybe it's not so big). What's with this mutual exclusivity? Don't you guys have a collection of console brands too? Alas, when I tire of 16 colors I'll have to play Atari, which is clearly the better value.

[Wolfram]

Yes. C64 graphics suffer heavily by the "depth" as regular systems did. The Atari can display depth and/or colours.

 

 

I guess nobody knows except you what are you talking about here.

[Wolfram]

I really should find the time for making other examples.... Those C64 blindflyers make me nervous...

 

Well this unfinished picture show 48 real colours per scanline... no interlace is used. Whre is anyhow anything compareable on the C64? 80 colour per scanline were also no problem.

 

 

indeed not comparable to c64.

 

 

here we can see some depth aswell.

[Fröhn]

The C64 was an advance because it DID use alternating phase for it's color. That's the only way to get to 320 pixels on a composite signal path.

320 px only for luma. On chroma you will not even get 160 px resolution (that's why you get strange edges with different chromas in that resolution too).

 

And A8 video signal is pretty much the same as the C64 one: The video chips generate a chroma carrier and luma based on the pixels they display. This causes "jumps" in the chroma wave because the phase is suddenly switched from one pixel to another. No NTSC/PAL device is able to decode that correctly, so you get a lot of side effects like shadows, artifacting and inaccurate edges when the chroma phase of two pixels is too different.

 

The 320 resolution of the C64 is simply switching luma & chroma at a higher rate. Luma will be visible, chroma will "mix" with strange results but that also happens on 160 px res. Chroma is VERY low resolution, but luckily the visibility of the luma is far stronger so people hardly notice it apart from the shadows I mentioned. As a little difference the C64 has a small filter added which reduces artifacting effects a bit.

[Wolfram]

Atari 80*240 256 REAL colours without interlace

 

With interlace 160x240 256 real colours

 

 

...

 

 

With interlace you can also reach the colour depth of the C64 .... easily toppping it.

 

real colors? like the c64 has fake colors ? I dont get it. A bit incorrect tho, for 256 colors you have to halve the resolution vertically.

[Fröhn]

real colors? like the c64 has fake colors ? I dont get it. A bit incorrect tho, for 256 colors you have to halve the resolution vertically.

Also: Every 2nd rasterline has to be close to black and the saturation is halfed because of chroma 50:50 mixing from one rasterline to another with every 2nd rasterline having no chroma signal. PAL only ofcourse, since NTSC doesn't do that rasterline color carrier mixing. It's a nice mode but not a perfect mode.