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Graphics modes 4, 6 and 14


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It's all about speed. 

fetching 20 bytes instead of 40 bytes per scanline .

 

It means, less CPU cycle stealing by antic, less ram to use , and in the result faster graphics for special purposes. 

Not sure what they had planned exactly back then. But the Atari was built for showing fullscreen action, particular 3d looking stuff. 

 

 

 

 

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20 minutes ago, emkay said:

It's all about speed. 

fetching 20 bytes instead of 40 bytes per scanline .

 

It means, less CPU cycle stealing by antic, less ram to use , and in the result faster graphics for special purposes. 

Not sure what they had planned exactly back then. But the Atari was built for showing fullscreen action, particular 3d looking stuff. 

 

 

 

 

thanks for that, I do understand there's speed difference, but still don't see any use for 1 colour modes with that resolution.

 

EDT: sorry, 2 colour modes.

EDT2: granted, Graphics 14's resolution might make this mode useful for something, but modes 4 and 6?

Edited by ac.tomo
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I don't have the exact numbers. 

But, if you have a real machine, you could write a small basic program, doing cycles and count the cycles for about  a minute or just 10 seconds.

Then activate all different graphics modes, and check how many cycles have been reached in every run.

 

It might give a clue. 

 

 

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They use less ram.  The 400 first sold with 4k and the 800 with 8k, so these modes probably were seen as useful at the time.  But ram quickly became less expensive and the ram saving modes became obsolete to a large extent - that's my guess.

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2 hours ago, ac.tomo said:

granted, Graphics 14's resolution might make this mode useful for something, but modes 4 and 6?

If you like to have a scenario that actually make sense, you can imagine a graphics 8 drawing program, which uses 4 and 6 for magnifying the content without touching the bitmap data.

Actually I planned to use those modes for a port of "Continuity" before "Ridiculous Reality" came out.

 

Remember "Jigsaws"? The nice title effect is possible thanks to those modes.

image.png.d0474c5085a49c8690ef896ebba79436.png

 

Your imagination is the limit...

Edited by Irgendwer
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12 minutes ago, Preppie said:

They use less ram.  The 400 first sold with 4k and the 800 with 8k, so these modes probably were seen as useful at the time.  But ram quickly became less expensive and the ram saving modes became obsolete to a large extent - that's my guess.

 

Those 2 reasons (speed and ram saving) are very good ones and your probably right (both of you, thats my guess too), but (I was just writing this reply when irgendwer responded) if anyone can think of a use for these modes I would be very interested, just out of curiosity. Thats a very good use, magnification, thats actually the reason I thought useful for modes 3, 5 and 7 (for mode 15), I didnt think of the 2 colour-mode magnification. Anyone have any more ideas useful for these modes?

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26 minutes ago, ac.tomo said:

Anyone have any more ideas useful for these modes?

Displaying QR-codes would also make sense.

Using these modes for big headlines while sticking to monochrome.

Esp. graphics 6 makes sense then: If you print text in it (e.g. in Turbo-Basic GR.6:C.1:TEXT 0,0,"Hello!") you have the same size like the characters in graphics 2 without the restriction for 64 chars only, but can print any character also in inverse video...

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They don't HAVE to be 2 colors only, if you use Display List Interrupts!  And you certainly don't need the entire screen to be in these modes, thanks to Display Lists.


Also, say you wrote a high resolution (GRAPHICS 8, 320x192) image editor / paint program.  These modes would give you 2x, 4x, and 8x zooms, basically at no cost!

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On 3/28/2021 at 2:07 PM, ac.tomo said:

Does anyone know the point of these modes, I can see a reason for modes 3, 5 and 7 but not these.

 

Don't judge 1978 decisions by 2021 standards.

 

I made good use of Gr.6 in my Tron recognizer demo (look left).

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On 4/4/2021 at 4:43 AM, ClausB said:

 

Don't judge 1978 decisions by 2021 standards.

 

I made good use of Gr.6 in my Tron recognizer demo (look left).

There's some good ideas here. That's a fantastic demo, I'd be very interested in the source code.

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Thanks. Attached are the source files. The demo runs on an 800 with the Axlon 128K RAMdisk installed, but the BASIC programs need only 40K.

 

PERSPECT.BAS draws the frames in perspective into a hidden GR.24 screen and then copies the central quarter into the visible GR.6 screen. This performs cropping of the images. It's a way around the DRAWTO errors you get if you draw directly into GR.6 and some lines go outside the bounds. It also copies the cropped image into a disk file called X, which accumulates frames for the 8 Axlon banks. Halfway through, it waits for a disk swap (I had only one 810) and continues with a new X file. If you would rather watch the GR.24 drawing progress, then delete line 37 before you RUN.

 

SOUND.BAS mocks up the accompanying sound effects.

 

GO.SRC is the page flipper and sound generator for run time.

 

xTRON1.ATR

 

EDIT: Guess I posted this before:

 

Edited by ClausB
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1 hour ago, ClausB said:

The earliest machines sold with 8K or 16K, so GR.8 wasn't practical as it took up 8K alone. Also many users, like myself, had only a B&W TV, so GR.6 was useful and took up only 2K.

Tell me about it.  Dad & I typed in Caves of Ice in 1982 with my 400 with b-key.  Saved it to 410 tape and took a while to debug the damn thing because we didn't have a printer either.  When we finally got rid of the errors, voila.  Error 2 :(  We did not do the 48kB upgrade.  I sadly have no idea of finding out who did the upgrade or what it cost.

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3 minutes ago, ClausB said:

Now GR.3, that's useless, with only 40x24 big, blocky pixels. I suppose it was there for those early 2600 game ports.

Yeah -makes sense when you consider the 2600 playfield.  What - 20 bytes, reflected or mirrored?  40 pixels was a luxury I tell you.

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On 4/11/2021 at 9:52 PM, ClausB said:

The earliest machines sold with 8K or 16K

During the design phase, it was thought that base machines would have only 4K RAM, so graphics modes with a minimal RAM footprint were even more vital. GR.3 plus low-res PMGs & OS reserved RAM leaves under 2K for program/data in a 4K machine....

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4 hours ago, drpeter said:

During the design phase, it was thought that base machines would have only 4K RAM, so graphics modes with a minimal RAM footprint were even more vital. GR.3 plus low-res PMGs & OS reserved RAM leaves under 2K for program/data in a 4K machine....

Yes, indeed:

 

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