800&XL/XE graphic modes ANTIC&CTIA/GTIA

[Gunstar]

Ok, I know that the XL/XE machines have a few graphic modes that the 800 does not, I think it was just GTIA modes 9, 10 and 11 that the CTIA didn't support, and I was looking for some info about this but haven't been able to locate any thus far. I want to upgrade my 800 so that it has these modes and need to know if it was the Antic or GTIA that does this(chances are I already have upgraded it, see below). I was looking inot IDE interfaces and know that I can get a custom one for the 800 from the person that does the MyIDE mods, that also adds these graphic modes to the 800. But, I'm not itnerested in an IDE for my 800, only my XL/XE's. So, I'm wondering if replacing either the ANTIC or GTIA in my 800 with a newer version will do this. I already swapped out the old non-working CTIA chip in my 800 with the GTIA in my 1200XL and have a replacement on the way for the 1200XL, so I might already have the newer modes with the GTIA chip installed, but IIRC, 800 with GTIA still didn't have the newer modes, which make me think it's the ANTIC that needs to be upgraded. Of course, while attempting to figure out what was wrong with my 800, I also swapped out ANTIC chips; the old NTSC ANTIC I had laying around after doing a PAL ANTIC conversion to my 1200XL, so maybe I already have the new modes in my 800 now? How can I tell? Is there a PEEK/POKE cammand or some other instruction I can type in Atari Basic to find out if I have the newer modes or not? What modes were they? Or was it only the XE's that had the newer graphic modes and the XL's are the same as the 800? I'm pretty sure it was just a CTIA/GTIA thing, but I just don't remember. Or is it something else entirely? Any info&links would be appreciated, or the different IC revision numbers of the ANTIC&GTIA between the 800/XL/XE computers. Also though, are there different revisions of the ANTIC chip that have differences about them? Different revisions of the GTIA chip with differences?

Edited June 20, 2005 by Gunstar

[analmux]

maybe the 800 OS doesn't know how to generate graphics 9,10 and 11 screens, but these have the same Dlist as gr. 8.

 

Try to draw something in gr. 8 and then do this:

 

poke 623,64

or

poke 53277,64

 

you may try to poke 128 or 192 instead of 64, or 0 to switch to normal screen.

 

As you may read in technical documents GTIA has 'GTIA-modes' (Duh!), these can be accessed by writing to address 623 (Shadow GPRIOR) or 53277 (GPRIOR)

 

0 = normal mode

64 = graphics 9 mode (shades)

128 = graphics 10 mode (9 fully controllable palettes)

192 = graphics 11 mode (colors)

[Goochman]

Only the initial 800s had CTIA chips in them - otherwise they were shipped with the same GTIA chip found in the XE's - I believe the only 'real' change was a supported call to get to the 'extra' graphics modes in the XL/XE OS but it is possible to get to these modes on the 800.

 

Im sure someone will correct me here

[+CharlieChaplin]

Afaik,

there is no need to replace Antic or GTIA in an Atari 800. They have all graphic modes available. It is the software - especially Atari Basic (Revision A cart. for the 800) that does not have gr. modes 12-15 available. But *again afaik*, with Assembler for instance one could still force an Atari 800 to use / display gr. modes 12-15...

 

Thus, when Atari advertised the XL computer line with new gr. modes, it was actually the built-in Atari Basic that did have new graphic modes. The graphic chips (Antic and GTIA) were and still are the same as in older Ataris... -Andreas.

[Schmutzpuppe]

You only need a GTIA for all modes the only difference is that you can’t use the GTIA modes with the basic command GR.

[Schmutzpuppe]

Ups that was quick when I read the question there was no answer

[analmux]

 

I've never seen this before: 4 people posting at the same time in the same thread:

[Gunstar]

thanks guys. I will type int those commands just to doublecheck, but I think my 800 is fully equiped now, then, since I switched out the CTIA with the GTIA and I guess it doesn't make a difference that I swapped out the NTSC ANTIC from my 1200 with the NTSC ANTIC that was in the 800 to start with, since they seem to be the same from what you guys have said.

[Gunstar]

 

I've never seen this before: 4 people posting at the same time in the same thread:

877760[/snapback]

 

yes, I was very suprised, I left the post, right away I edited it to add some more info of what I did recall, and when I posted the edit, I already had several responses!!!

[Gunstar]

I did the poke commands and I definately have modes 9, 10 and 11, pretty cool to see text in those modes, even though 10 and 11 are completely unreadable, I could still make out the text in mode 9 with the shades of grey...cool. So, my 800 has all the available modes, oh, and by the way to Charliechaplin; the origianl revision A basic can use the modes, as well as the original 10k OS, becuase that is what I have in my 800 right now while I did the poke tests, so I think it was just the difference between the CTIA and GTIA chip, nothing else. I guess I have the full pallette of 256 colors with the GTIA too, right? It was the CTIA that only haad 128 color pallette?

[Goochman]

GTIA had 256 color pallete and the 16 color mode in 9,10,11 - CTIA didnt really have much for those modes IIRC.

[analmux]

I don't understand. I have an atari 800 xl at home, with a GTIA chip, and the palette has only 128 colors ??? Except for graphics 9: here I have 16 shades of only one color, but in other modes the palette has only 128 colors!

[deathtrappomegranate]

PAL GTIA and ANTIC chips have a colour bug. Whereas the NTSC versions have a palette of 16*16=256 colours, the PAL chips have one colour missing, and a palette of 15*15=225 colours.

[Foebane]

I think this is how it is with all Atari 8-bits. Only 128 colours are available (16 colours at 8 shades each) on all modes except for GR.9 and GR.11, where it's shades and colours respectively, but not in any way combined.

 

Although, combination is possible by alternating between 9 and 11 on successive scan lines, and some demos and software have just done that for some amazing colourful 256 colour visuals.

[analmux]

Well, Gr.11 doesn't provide 16 colors at one of 16 shades either: you can only choose from 8 shades. So gr. 9 is the only mode providing 16 shades of one color. Indeed those mixed gr.9/11 graphics can show 256 colors, but when you want to select 9 independent setcolors from the palette you have only 128 colors to choose from.

 

PAL GTIA and ANTIC chips have a colour bug. Whereas the NTSC versions have a palette of 16*16=256 colours, the PAL chips have one colour missing, and a palette of 15*15=225 colours.

 

Which color would that be, missing on PAL chips? Maybe colors 1 and 15 are very close to each other (the same for colors 7 and 8 ) but there IS a difference.

 

Furthermore, my PAL a8bit has 16 shades in every available color.

Edited June 20, 2005 by analmux

[deathtrappomegranate]

Which color would that be, missing on PAL chips? Maybe colors 1 and 15 are very close to each other (the same for colors 7 and 8 ) but there IS a difference.

 

Furthermore, my PAL a8bit has 16 shades in every available color.

 

In gr11 I've found that the first and last colours are the same. Similarly, in gr9, it looks like there are only 15 shades, and not 16.

 

I've seen this on different machines.

 

However, I haven't done any detailed analysis on it.

[analmux]

Which color would that be, missing on PAL chips? Maybe colors 1 and 15 are very close to each other (the same for colors 7 and 8 ) but there IS a difference.

 

Furthermore, my PAL a8bit has 16 shades in every available color.

 

In gr11 I've found that the first and last colours are the same. Similarly, in gr9, it looks like there are only 15 shades, and not 16.

 

I've seen this on different machines.

 

However, I haven't done any detailed analysis on it.

877835[/snapback]

 

(I've had a better look)

Yup, color 1 and 15 are practically the same. Furthermore I've noticed that shades 0 and 1 are so dark they look the same, but when you turn up the monitor brightness a little you actually see difference.

 

So we have a total of 15 colors with 16 shades in gr.9 or 8 shades in other modes = 120 or 240 colors.

[kenfused]

Afaik,

there is no need to replace Antic or GTIA in an Atari 800. They have all graphic modes available. It is the software - especially Atari Basic (Revision A cart. for the 800) that does not have gr. modes 12-15 available. But *again afaik*, with Assembler for instance one could still force an Atari 800 to use / display gr. modes 12-15...

 

Thus, when Atari advertised the XL computer line with new gr. modes, it was actually the built-in Atari Basic that did have new graphic modes. The graphic chips (Antic and GTIA) were and still are the same as in older Ataris...  -Andreas.

877754[/snapback]

The XL/XE OS actually provides the extra graphics modes (to BASIC). All BASIC does is call CIO functions to pick the mode, plot points, draw lines so it does not matter if you use an original BASIC cart on an XL or XE, you will still get the graphics modes. Very few programs other than BASIC (Or ACTION) are going to access the graphics through the OS though due to speed. The graphics modes not available on 400/800s are 12 (antic text mode 4) ,13 (antic text mode 5), 14 (160x192 in 2 colors), and 15 (160x192 in 4 colors)). The hardware does support the modes though so ML programs/routines can access them.

 

This is not be confused with GTIA graphics modes 9,10,11 are available to 400/800's provided they have the GTIA chip.

[ijor]

Well, Gr.11 doesn't provide 16 colors at one of 16 shades either: you can only choose from 8 shades. So gr. 9 is the only mode providing 16 shades of one color. Indeed those mixed gr.9/11 graphics can show 256 colors, but when you want to select 9 independent setcolors from the palette you have only 128 colors to choose from.

 

Graphics 9 is the only mode that can realize the 256 colors palette.

 

In all other graphics modes (and player-missile) the luminance is selected using the lower nibble COLOR GTIA registers which is 3-bits only. Graphics 9 is unique in that the luminance is provided by Antic from the screen data.

 

You don't need to mix 9/11 modes to get 256 colors, nor it will be very useful. You use DLI's with multiple gr. 9 scan zones.

[Gunstar]

Well, Gr.11 doesn't provide 16 colors at one of 16 shades either: you can only choose from 8 shades. So gr. 9 is the only mode providing 16 shades of one color. Indeed those mixed gr.9/11 graphics can show 256 colors, but when you want to select 9 independent setcolors from the palette you have only 128 colors to choose from.

 

Graphics 9 is the only mode that can realize the 256 colors palette.

 

In all other graphics modes (and player-missile) the luminance is selected using the lower nibble COLOR GTIA registers which is 3-bits only. Graphics 9 is unique in that the luminance is provided by Antic from the screen data.

 

You don't need to mix 9/11 modes to get 256 colors, nor it will be very useful. You use DLI's with multiple gr. 9 scan zones.

877855[/snapback]

I beg to differ about mixing graphics 9 and 11 not being very useful, there were several paint programs; Technicolor Dreams, ApacPaint (shareware) and EscalPaint(?) that allowed these mised modes for wonderful 256 color graphics and even a picture viewer program by Jeff Potter called APACview which had an interlaced mode of graphics 9&11 to get a 80x192 res screen with 256 colors and it was wonderful. I'm trying to track down these programs again right now, and just mentioned them and others, in the thread TGX/mnx started about the jpeg viewer program. My point is, it's more useful to me as an artist, then even the DLI's are that I also use quite often with paint programs like Rambrandt. mix of 9/11 is VERY, VERY, VERY USEFUL!!! :!:

[Heaven/TQA]

ijor... isn't a nible 4 bits so the lower 4 bits of the colour register?

(0-15)

 

i mean if you write a small test DLI you can have the 256 rainbow colours on screen? so not 128... or am i wrong? i never understood these 128 colour discussions at all...

 

ldx #0

loop stx $d40a

stx $d01a

stx $d018

inx

jmp loop

[danwinslow]

Its spelled nybble, and its 4 bits. Thats pretty much all I have to add to this discussion, so I'll shut up now.

[emkay]

Has anyone an idea, why the 16 luminances are only available with the GTIA modes?

Perhaps the real pallette is 128 colours only?

Remembering that only Gr. 10 has 9 colours with an adjustable pallette register and the 128 colours.

While Gr. 9 has 16 luminance steps and GR. 11 has 16 colours, they can be used by interlace or flicker to gain 256 visible colours on screen.

 

The registers can be set in 16 steps, but the brightness changes every 2nd step only. GTIA has no problem with 16 luminances and the control for 16 luminances is still there.

So: Why are only 8 luminance steps possible without the GTIA modes?

Is there a design bug in the hardware that I do not know?

Edited June 21, 2005 by emkay

[Bryan]

I have no idea why Atari put 4 LUM pins on GTIA and then didn't support them in all modes. What I really wish is that Atari had made 15 shades available and made the lowest LUM setting shut off the color output (black). This way we could have had colored text on a black background.

 

-Bry

[ijor]

You don't need to mix 9/11 modes to get 256 colors, nor it will be very useful. You use DLI's with multiple gr. 9 scan zones.

877855[/snapback]

I beg to differ about mixing graphics 9 and 11 not being very useful,

... My point is, it's more useful to me as an artist, then even the DLI's are that I also use quite often with paint programs like Rambrandt. mix of 9/11 is VERY, VERY, VERY USEFUL!!! :!:

878128[/snapback]

 

Sorry. What I meant is that mixing gr. 9 and 11 is not very useful for the specific purpose of displaying 256 colors. Of course it can be useful for many other things.

 

The only practical way to display 256 colors is to have 16 or more bands of graphics 9, each of them with a different HUE set by a DLI. It is probably feasible to use cycle counting and change the HUE color in the middle of a scan line. That would work instead of DLIs. But it still must be done with gr.9.

 

Using flicker or artifacts to get "visually" more colors is a completely different thing. We are talking about displaying the whole GTIA 256 colors palette.

 

ijor... isn't a nible 4 bits so the lower 4 bits of the colour register?

 

Yes, but bit 0 of these registers is ignored. More than likely this “bit” doesn’t exist in the hardware.

 

Why are only 8 luminance steps possible without the GTIA modes?

 

Again, this way of phrasing is a bit misleading. The difference is not exactly between GTIA modes and CTIA modes. What makes possible the 256 colors on gr.9 (and again, only in gr.9) is the fact that the “luminance” registers are not used.