Is it possible to have colored text like a C64?

[Gunstar]

The problem with Atari was that they didn't really do anything new aside from the ST in the 1980s.

 

The XL and XE were progressive upgrades that didn't exactly require engineering genius. 5200 just a cutdown 400, 2600jr just natural progress of smaller componentry.

 

And the 7800, Jag and Lynx were picked up from outside sources and just packaged and marketed by Atari (albeit rather badly marketed).

 

 

As for extra text capability - they would have done well to have left out the descender mode (3) and used it instead as a special "colour buffer" mode.

 

Use the first scanline to read in background colour information and buffer it, second scanline for foreground colour information and buffer it.

 

Then have a normal 8 lines of Gr. 0 mode, using the previously buffered colour information allowing any combination of bg/fg colour per character cell.

 

Problem is, they would have needed a workaround for the 2 luminences of 1 colour problem.

 

your right about all those systems except the Jaguar. Yes, it was done by an outside development house, Flare 2, but it's design was directly influenced by Atari and not just marketed by them after it was done. The Jaguar probably would have been BETTER if Atari hadn't had a hand in it and let FLARE 2 fully design it themselves and Atari just market it. For instance, the bottle-necking 68000 was Atari's idea to give programmers a "warm fuzzy feeling" with known hardware while starting development.

[Fröhn]

The method is a bit different. The 6510 is clocked at half the memory speed so that bitmap/charmap accesses are transparent,

Yes, exactly the same as on A8 when displaying bitmap data. And every 8 rasterlines the C64 and the A8 use the other cycles too for fetching char matrix data. It`s exactly the same.

 

and in character mode the colour nybbles are synchronous with the character matrix pointers.

In hires bitmap mode on C64 the color nibbles are not even used. You could do EXACTLY the same gfx mode on A8 with the data the A8 already fetches in 8x8 character mode.

[Gunstar]

I think it would have been a simple thing for Atari to have had absolute black (or 0 luminance) as one of the possible 16 shades of each color's luminance(when designing the GFX chip), then we could have had multi-color text easily on at least a black background. Is that something that could be programmed? I mean, out of the 128/256 colors white has black as a shade, why not the others? Becuase the real problem here, it seems to me, is not that the Atari can't print color text, it can(one color at a time), with more color choices than the C64, but you have to deal with the color bars of a different shade(the background). With display list interupts and VBI's full color text could be reached on a black background. Sure the C64 would still have the advantage of multi-color text with whatever color background, but it would be a big improvement for the Atari in that area if full color text could be displayed on a black background. A screen like the one I posted above in Antic mode E could be done with mode 2 text(with a black background in the text windows instead of grey).

[supercat]

I think it would have been a simple thing for Atari to have had absolute black (or 0 luminance) as one of the possible 16 shades of each color's luminance(when designing the GFX chip), then we could have had multi-color text easily on at least a black background.

 

Medium-blue text on an almost-black blue background will show up much better than medium-blue text on a black background. The color generation circuitry in a typical monitor will have trouble accurately displaying a color which is displayed for less than two "mode 0" pixels. The color restrictions of the high resolution modes exist because of that; it was almost certainly felt that there was little reason to allow the Atari 800 to generate colors that monitors would be unable to display well or consistently.

[Gunstar]

I think it would have been a simple thing for Atari to have had absolute black (or 0 luminance) as one of the possible 16 shades of each color's luminance(when designing the GFX chip), then we could have had multi-color text easily on at least a black background.

 

Medium-blue text on an almost-black blue background will show up much better than medium-blue text on a black background. The color generation circuitry in a typical monitor will have trouble accurately displaying a color which is displayed for less than two "mode 0" pixels. The color restrictions of the high resolution modes exist because of that; it was almost certainly felt that there was little reason to allow the Atari 800 to generate colors that monitors would be unable to display well or consistently.

 

Well doesn't the C64 use a similiar high resolution mode for their color text (as far as how man pixels wide a character is)? Why wouldn't C64 high-res text have the same restrictions? The C64 uses the same type of monitors. I understand your line of reasoning, but it seems to me to be obviously flawed since the C64 DOES have colored text in a similiar resolution to the Atari's high-res monochrome text.

Edited March 18, 2007 by Gunstar

[supercat]

Why wouldn't C64 high-res text have the same restrictions? The C64 uses the same type of monitors. I understand your line of reasoning, but it seems to me to be obviously flawed since the C64 DOES have colored text in a similiar resolution to the Atari's high-res monochrome text.

 

On older C-64s, colored text really didn't look all that wonderful. The newer C64s alternated chroma phase every scan line and every frame, thus ensuring that things would "average out" to the right colors.

[Gunstar]

Why wouldn't C64 high-res text have the same restrictions? The C64 uses the same type of monitors. I understand your line of reasoning, but it seems to me to be obviously flawed since the C64 DOES have colored text in a similiar resolution to the Atari's high-res monochrome text.

 

On older C-64s, colored text really didn't look all that wonderful. The newer C64s alternated chroma phase every scan line and every frame, thus ensuring that things would "average out" to the right colors.

 

I see, well I think that's something that could be done on the Atari as well, along with what I suggested above. Besides, the older C-64's colored text was still better than monochrome wasn't it? Even if not perfect.

[ijor]

I don't know what the C64 can do, but I think we are talking about two different things.

 

One thing is to display two different hues in the same color clock (two contiguous pixels on high rez). That indeed presents a problem for older TVs and for the RF/Video color bandwidth.

 

But another thing is to have a mode with multiple hues on the same line at high rez, just not in the same color clock. That wouldn't represent any problem from the video point of view.

[emkay]

I don't know what the C64 can do, but I think we are talking about two different things.

 

One thing is to display two different hues in the same color clock (two contiguous pixels on high rez). That indeed presents a problem for older TVs and for the RF/Video color bandwidth.

 

But another thing is to have a mode with multiple hues on the same line at high rez, just not in the same color clock. That wouldn't represent any problem from the video point of view.

 

Hm....

You know, that the 800 has SVIDEO capabilities already?

The only TV System that had problems with the "hires" colours was/is NTSC.

PAL TV with separated brightness and colour signals, can display "hires colours" from the start.

 

The colour and brightness generation is sparated in the ATARI's circuitry. So, why the heck, did they switch off the colour creation, when using hires?

To prevent colour mixing, there still was the ability to use the brightness of one colour by the pallete.

[ijor]

PAL TV with separated brightness and colour signals, can display "hires colours" from the start.

 

So you mean that Atari should have designed a mode that would be usable only on PAL system with Svideo? That doesn't sound too realistic, does it?

 

The colour and brightness generation is sparated in the ATARI's circuitry. So, why the heck, did they switch off the colour creation, when using hires?

 

The real reason (I suppose) has nothing to do with the external video, but with the chipset. Using multiple colors in high rez would need a chipset redesign. The whole Antic/Gtia concept is about color clocks. Hirez modes work completely different.

[Rybags]

The C-64 gets chroma distortion/aliasing artifacts just as the Atari (probably worse). The workaround is that virtually all characters always have at least two pixels adjacent of the same setting (0 or 1).

 

The Atari also has to work from the base clock frequency (1.79 MHz), and use internal delays.

 

Doesn't the Vic-II work on a higher clock (like 4 or 8 MHz) from the start?

[pseudografx]

The C-64 gets chroma distortion/aliasing artifacts just as the Atari (probably worse). The workaround is that virtually all characters always have at least two pixels adjacent of the same setting (0 or 1).

 

The Atari also has to work from the base clock frequency (1.79 MHz), and use internal delays.

 

Doesn't the Vic-II work on a higher clock (like 4 or 8 MHz) from the start?

AFAIK it's even something like 17 MHz, which is quite a frequency for a machine of that time. I'm not into electronics, but I quess this high frequency is also the reason why VIC-II doesn't steal as many cycles as Antic.

[Fröhn]

The C-64 gets chroma distortion/aliasing artifacts just as the Atari (probably worse). The workaround is that virtually all characters always have at least two pixels adjacent of the same setting (0 or 1).

Yes, the Commodore font uses that "trick" to make artefacts disappear. There are custom fonts not doing that though.

 

Doesn't the Vic-II work on a higher clock (like 4 or 8 MHz) from the start?

Yes, the A8 uses 7,09 MHz pixel clock, the C64 uses 7,88 MHz (both on PAL systems).

NTSC: 7,16 MHz on A8, 8,18 MHz on C64.

 

This means: An alternating of black and white pixels gives a frequency of 3,55 MHz on A8 and 3,94 MHz on C64. So C64 is a lot closer to the 4,43 MHz color carrier and the filter will carry more of the black/white pixels into the color carrier.

 

BTW, I have seen the C64 bashed for not having square pixels. Well, A8 doesn't have square pixels either. On C64 the pixels are about 5% too tall, while on A8 the pixels are 5% too wide.

[supercat]

The C-64 gets chroma distortion/aliasing artifacts just as the Atari (probably worse).

 

The older NTSC ones did. The newer ones mitigate them by alternating the color phase on every line and every frame.

 

The newer Commodore 64 generates one system clock cycle every 3.5 ticks of the color clock; a scan line of 65 clock cycles will thus take 227.5 color clocks which is the precisely correct value for broadcast NTSC.

 

The Atari outputs generates one system clock cycle every two ticks of the color clock; a scan line of 114 clock cycles will thus take 228 color clocks.

 

Perhaps it would have been better if the Atari had somehow figured out a way to jinx the color phase each line, but the only way I can really see to have done that would have been to output 113 system clock cycles per line, followed by a 1.5 cycle 'dead time'.