Why 5 different text modes on the Atari family computers?

[punchy71]

I was looking at the specifications of the entire Atari 8-bit family line of computers and I noticed that they all have five (count them; 5!) text modes at a time when most 8-bit machines only had one text mode (2 if you were lucky)! The modes range from a minimum of 20 characters by 12 rows to a maximum of 40 characters by 24 rows. That is all I know from my research so far. I can't find anywhere on the internet what the other three modes were. Can someone please inform me what they are?

Also, why did Atari do this? Why would anyone need or want or use five different text modes? What was the purpose? Did anyone make use of the different text modes? Did anyone make use of the 20x12 mode (the lowest)? And why? Most other 8-bit machines had a 40 column mode and if you were lucky, an 80 column mode.

Puzzled...

 

Thank you

[sloopy]

The other text modes were used for a variety of things, with the way the video is done in the atari 8bit computers, you arnt limited to a screen of just one mode (of 15), but can use different modes on different lines... So having a title bar at the top with a 20col mode and then having text info at 40col mode underneath it, is common...

 

you may want to throw an eyeball through 'De Re Atari' a book that describes the modes pretty well, to get an idea of the basic capabilities of the ANTIC/GTIA in these machines...

 

sloopy.

[Rybags]

Why not? C64 has 3 - normal, multicolour and extended background colour modes.

 

Atari actually has 6 text modes, not counting "special" ones you can get with software tricks.

 

We have the normal Gr. 0 aka Antic 2. 8x8 hires pixels.

Antic 3 "descender" mode. 8x10 hires, allows the lower case characters to have descenders on letters like g and j

2 multicolour modes with 5 available colours (4 per cell) with 2x1 or 2x2 equivalent resolution.

2 modes with 2x1 or 2x2 sized pixels with 1 of 4 foreground colours per cell.

 

Throw in the useful GTIA variations and you end up with another 3 based on GTIA modes and Gr. 0

Edited December 20, 2011 by Rybags

[R6502A]

I would have given those modes up, except gr.0 & gr.12/13, for a standard 80 column multicolour mode.

[+Stephen]

Keep in mind, that the video chip only has 40 bytes per line to play with (48 in wide mode). So, that means 40 characters, 320 monochrome pixels, 160 4 color (2-bit) pixels, 80 16 color (4-bit) pixels, etc. 80 column already exceeds the # of available bytes and throw in color and we are way over.

[emkay]

Keep in mind, that the video chip only has 40 bytes per line to play with (48 in wide mode). So, that means 40 characters, 320 monochrome pixels, 160 4 color (2-bit) pixels, 80 16 color (4-bit) pixels, etc. 80 column already exceeds the # of available bytes and throw in color and we are way over.

 

The video chip has just some colour abilites and PM objects.

The DMA Chip uses up to 48 bytes per scanline...

 

Atari always had the chance to enhance the video chip aka GTIA with own memory, to give real 80 columns and/or real 256 colour resolutions.

[Bryan]

The Atari computers have several horizontal and vertical resolutions, and they simply decided to allow you to use the character logic as well as the bitmap logic with various resolutions.

 

It's fairly common to see the "big text" modes on title screens and the multi-color character modes (mostly Antic 4) are used for building playfield graphics.

 

The bottom half of MULE's title screen combines high-rez text with 160-mode text (Antic modes 2 and 6).

[Lazarus]

Also, why did Atari do this? Why would anyone need or want or use five different text modes? What was the purpose? Did anyone make use of the different text modes? Did anyone make use of the 20x12 mode (the lowest)? And why? Most other 8-bit machines had a 40 column mode and if you were lucky, an 80 column mode.

The low resolution modes are probably there because the early A8 models had less memory (8k, 16k...), so modes with less memory usage were needed.

[SeaGtGruff]

Just a slight quibble-- I think "character modes" is more accurate than "text modes," since there's really only 4 "text modes" as far as being modes that display readable text. Or 3 if you discount the "descenders" text mode, since it requires special coding (shifting of the character data) to use, whereas the other 3 are readily usable for text "from the box." This is not to say you can't create text displays with the other 2 character modes, but you have to create a custom character set to do so.

[flashjazzcat]

It's worth remembering that these computers were commonly used with crappy old TVs via RF when they were first designed. I'd challenge anyone to read 80-column text on the 14" portable I used in the 80s.

Edited December 21, 2011 by flashjazzcat

[Bryan]

It's worth remembering that these computers were commonly used with crappy old TVs via RF when they were first designed. I'd challenge anyone to read 80-column text on the 14" portable I used in the 80s.

Yep. When you're designing a computer for TV use, 80-columns isn't a very high priority.

[ClausB]

It's worth remembering that these computers were commonly used with crappy old TVs via RF when they were first designed. I'd challenge anyone to read 80-column text on the 14" portable I used in the 80s.

 

In fact, I developed DT-80 (forerunner of ACE80) on my 400 with a 12" B&W TV, and its 80 columns were quite readable. Of course, the monochrome television had a higher luminance bandwidth, since it could ignore the color subcarrier signal.

[Tyrop]

I seem to remember that Atari gave a reason for the large text modes, eg, Basic's graphics modes 1 and 2, in one of the manuals or maybe one of the books on Basic. If I remember correctly, Atari's reason was something to the effect of titles, banners and labels. I also remember an early article, maybe in Compute magazine, that explained that Atari was one of the few computer of the time (maybe the only one circa 1981) that allowed the programmer to redefine the character set to create a custom font. As someone mentioned above, this a powerful capability, particularly in the multicolor modes, to create playfields. Many games also used redefined characters as sprites.

Edited December 22, 2011 by Tyrop

[flashjazzcat]

In fact, I developed DT-80 (forerunner of ACE80) on my 400 with a 12" B&W TV, and its 80 columns were quite readable. Of course, the monochrome television had a higher luminance bandwidth, since it could ignore the color subcarrier signal.

Mono helps. I guess it's a question of what you define as comfortably readable, and this is pretty subjective. The Last Word's 80 column fonts (effectively the same as Ace-80's) are still hard going even on a machine with tuned-up video and viewed through my 1084S-D2. They look great on a VBXE machine, though.

[peteym5]

I believe the reason for 20 column modes and low resolution modes was at the time Antic and GTIA were being designed, memory was much more costly. The orignal intent of CTIA/GTIA was for the next game machine from Atari, replacement for 2600. So the screen would not take up a whole lot of memory. When Atari seen home computer market opening up in the late 70s, they decided to split into two video chips and support text modes. I know Atari ordered thousands of these chips and probably why they kept using them rather than upgrading the video. By the time the 65XE and 130XE were released, memory was very cheap and they still had alot of chips stockpiled. Atari could have easily upgraded the video chipset at anytime, there was a proposal to combine GTIA and Antic into one chip when the XL series was being put together. That would have been a good point to add more abilities to the video, like 80 column support, Interlace mode, more onscreen colors at once. Atari would need the new single chip run at 7+ MHZ to double the color clocks per line. Could have been made backward compatible, have the enhancements switched on and off. There was plenty of space for more registers, The Antic Area had some unused memory locations.

 

There was also a proposed system to have to Maria (7800) chip in with a new 8-bit computer, but the Tremials took over and decided to go with the 16-bit ST. I am not sure if the Maria has character map text modes like the Antic does. I am not sure how the 7800 adresses the background graphics and sprites. Have a hard time finding programming guides for it.

[Rybags]

Maria has text modes but would have a hard time interfacing with the A8.

 

For starters it doesn't generate Refresh cycles and likely won't co-exist in a system that needs them (7800 uses Static RAM)

Also, to be of any use, the RAM has to be able to run at 7.2 MHz, so there's 2 big barriers against it.

 

GTIA/Antic split in the first place would almost certainly be due to not being able to fit everything on the 1 piece of silicon at the time.

Another possibility is due to GTIAs delayed arrival.

A third is that GTIA can function without Antic, so that could have allowed them to develop a cut-down replacement for Antic that could have teamed with GTIA in a cheap console.

[+wood_jl]

Several ***EXTREMELY KEEN AND SUPERIOR INTELLECTS**** have already chimed in, so I'm a bit sheepish to even type here. (You know who you are!!!)

 

But they used character-addressed modes for lots of games, unless I completely don't know what I'm talking about. They could redefine the pixels that form the letter "A" into a Space Invader, and then use a mode like that for a game, saving tremendous RAM (when 8K was available) in creating a graphic for a game. Big brains, is this not so? I'm starting to think that it's not, since I'm not sure it was mentioned, so I preemptively stand corrected. Aliens were bigger in some of the wider text modes.

Edited February 18, 2012 by wood_jl

[Rybags]

Yep, if you did a survey of all graphical games, character mode would probably come in over 75%

 

More modes gives more versatility, and indeed plenty of early games used lower res modes than could otherwise be possible as a RAM conservation measure.

 

The other thing is, the Display List arrangement allowed 14 combinations so they filled them all in. If anything, we should be questioning why so many bitmap modes. OS mode 3 is kinda pointless and so is 4 and to a degree 6.

 

Thanks to Gr. 3 they gave HSCROL 16 positions which in itelf is handy but creates a big DMA penalty with the higher resolution modes.

[peteym5]

If Atari built a system around the Maria (7800 graphics) chip, they would had to rewrite sections of OS that involved graphics and screen editing and would not be backward compatible with the XL/XE. All the low-res modes be elimiated and have 40 column only text modes. That along with using the faster ram chips.

 

Now I look at many games on the 8-bit, don't recall anything using the low modes. Almost everything is 5 color character map or 160 wide pixel bitmap. See a few using Antic 2 or 320 wide 2-color bitmap. I like using Antic 3 custom fonts for the scoreboxes and in game texts because I can make characters 8 pixels tall with 2 pixels between them. The 20 column 4 color modes are also useful for big character score boxes. Remember alot of people played games on their analog small screen television sets while sitting 10 feet away on a couch. Why the 8-bit needed those character modes.

[Gunstar]

In fact, I developed DT-80 (forerunner of ACE80) on my 400 with a 12" B&W TV, and its 80 columns were quite readable. Of course, the monochrome television had a higher luminance bandwidth, since it could ignore the color subcarrier signal.

Mono helps. I guess it's a question of what you define as comfortably readable, and this is pretty subjective. The Last Word's 80 column fonts (effectively the same as Ace-80's) are still hard going even on a machine with tuned-up video and viewed through my 1084S-D2. They look great on a VBXE machine, though.

 

Really? I've found your TLW 80 column extremely sharp and clear, even with the color all the way up, though of course there's no reason so I leave the color at 50% and it's very sharp and clear. I'm using 1200XL with SuperVideo 2.1 for chroma/luma on my 1084S-P. I'm so impressed with the clarity that I'm now using my 1200XL as my only wordprocessor (I'm writing a novel) and feel absolutely no need for something like an XEP-80 or even the VBXE for 80 columns (though I'd like it for many other reasons).

Edited February 19, 2012 by Gunstar

[emkay]

I believe the reason for 20 column modes and low resolution modes was at the time Antic and GTIA were being designed, memory was much more costly. The orignal intent of CTIA/GTIA was for the next game machine from Atari, replacement for 2600. So the screen would not take up a whole lot of memory. When Atari seen home computer market opening up in the late 70s, they decided to split into two video chips and support text modes. I know Atari ordered thousands of these chips and probably why they kept using them rather than upgrading the video. By the time the 65XE and 130XE were released, memory was very cheap and they still had alot of chips stockpiled. Atari could have easily upgraded the video chipset at anytime, there was a proposal to combine GTIA and Antic into one chip when the XL series was being put together. That would have been a good point to add more abilities to the video, like 80 column support, Interlace mode, more onscreen colors at once. Atari would need the new single chip run at 7+ MHZ to double the color clocks per line. Could have been made backward compatible, have the enhancements switched on and off. There was plenty of space for more registers, The Antic Area had some unused memory locations.

 

There was also a proposed system to have to Maria (7800) chip in with a new 8-bit computer, but the Tremials took over and decided to go with the 16-bit ST. I am not sure if the Maria has character map text modes like the Antic does. I am not sure how the 7800 adresses the background graphics and sprites. Have a hard time finding programming guides for it.

 

 

It's all nuts about missing upgrades for the A8. It would have been so easy to them, to upgrade the GTIA. Particular the "unused" low res modes could have been used as an initial for GTIA(extended) doing an overlay over the DMA resolution, doing new char modes, reading the content from extra Video RAM. Also the PMg could have easily been upgraded then.

But, to be honest. The real lacks in the A8's design is the limited moving objects, and the rubbish Audio. We shouldn't forget the design was built in the 70s, but doing NO upgrades at all..... how would someone name it .... nuts isn't the best term. In german we say "plem plem" .

No changes on the "base" of the machine have been needed, as many GTIA registers have been unused. Only some changes on the chip design were needed, to make the A8 a full 80s computer and 100% compatibility to the 400/800.

[peteym5]

Something I thought was dumb with the 7800 was not having an onboard Pokey chip, all the sounds had to come from the onboard TIA. If that had a Pokey (or Gumby) with 4 voices, plus 2 more TIA, Atari would have a competive system to the NES. But do agree Pokey could have been replaced with something with more abilities at some point, FM Sound, different wave forms, more voices, PCM, etc. Many on here agree the ST sound chip with only 3 sound voices was a drawback also, not much better than Pokey or SID. I don't see why anyone didn't make sound chips with 8 or more voices in the mid 80s. Later chips also started ran independant speed from the bus.

 

On the Atari 7800 vs Nintendo NES and Sega Master system, it was a lack of promoting the 7800 on Ataris' part that hurted them also (Atleast in the United States.) Many did not even know Atari made the 7800 here, but we were seeing TV commercails for Nintendo all over the place. Graphicly it was more capable than the other 2 systems. Would take a 16 bit system (like Sega Genesis/Megadrive) to exceed it. Atari still owened copyrights of their arcade titles that they did not allow to be ported to other systems. Plus these companies were trying to bash each other with other legal licensing agreements.

 

Atari probably held up upgrading the Antic/GTIA because 16 bit technology was in development. The people who made the 8-bit left Atari Corp. and started to make what would become the Amiga. Think Atari invested in the Amiga before Commodore bought them out. If Atari waited past 1983 to produce an upgrade to their 8 bit system, they would have been swamped with 16 bit systems within a year anyway.

Edited February 19, 2012 by peteym5

[emkay]

IBM PC is the best example of how it goes.

And Atari had the same chance , but missed it like trying to catch a fish in the desert

8 bits were not dead long time after 83. And the A8's CPU were still stunningly fast for the early 80s.

 

And, well, TIA.... why ... the heck.... did they remove the sound capabilites out of the GTIA. Just adding a slight programmable counter in there .... "start ... end ... speed .... loop " ... and voilá ... a full pcm for basses had been born. POKEY is able to push the rest of the music well.

There really wasn't much to do (related to the overall development)....

[emkay]

The interesting point here....

Atari always looked at the A8 like some "side prod" . But, everytime the actual owner searched for a gain on the market, the A8 was thown there... with just some optical changes.

[flashjazzcat]

I've found your TLW 80 column extremely sharp and clear, even with the color all the way up, though of course there's no reason so I leave the color at 50% and it's very sharp and clear. I'm using 1200XL with SuperVideo 2.1 for chroma/luma on my 1084S-P. I'm so impressed with the clarity that I'm now using my 1200XL as my only wordprocessor (I'm writing a novel) and feel absolutely no need for something like an XEP-80 or even the VBXE for 80 columns (though I'd like it for many other reasons).

 

That's great! I suppose because I'm used to RGB output on a couple of my machines, I'm more critical of the Y/C signal. I find the uprights on the 4-bit characters tend to be of uneven width even on my carefully tuned 800XL when used with a 1084S-D2. This is also true of the s-video decoders on several of my older LCD TVs. More modern LCDs tend to do a better job with s-video, though, so I can't say for sure if the issues are inherent to the s-video signal itself.

 

It does my heart good to hear you're writing a novel on your 1200XL! I did the same on my 65XE about fifteen years ago (must dig the floppies out some time and reacquaint myself with how bad it was!).