Why no custom resolutions on the ST? (Engineering reasons?)

[Xebec]

Why exactly aren't there more variety in resolution/color options on the ST?

 

Was the ST Shifter chip simply too limited? Would there have been relatively easy changes that would have enabled some customization of resolutions?

 

I know there are overscan techniques, ways of getting more colors per line -- but why not actual fundamental and native different resolutions?

[ParanoidLittleMan]

Really expecting it in machine designed in 1984 ? It was made to be usable on regular televisions. What dictated border, frequencies and even max resolution. And ST added on it monochrome mode for serious work, in time were monitors were expensive. Another limiting factor was RAM - that's why max 16 colors. They could add more colors at price of slower work. That happened with TT and Falcon. End of story.

[krupkaj]

Yes why not, for example Atari 800 is very flexible. There are 3 steps in width 256/320/400 pixels (highrez). And with ANTIC display list you cen set up any number of lines. You must be just careful what TV can display.

 

It is a pity it is not possible to use overscan on ST some simple way. And unfortunately the LaceScan addon does not work with STE.

Edited March 8, 2018 by krupkaj

[tjlazer]

You would think with updated TOS it would provide more resolution options like the Amiga did even on 1985 hardware. Seems like an OS limitation?

[MrMaddog]

I dunno, you can increase the resolution in emulators but it makes the graphics draw slower. Either because it uses main memory for it's video RAM and/or the GEM routines were unoptimized resulting in the need for something like NVIDI.

 

I remember there were plans for the STe to have an increased video mode but it required a 68030 chip, so only TT's & Falcons got the extra resolutions.

 

Also the mouse moves the same speed across the now larger desktop making it feel slower, probably why Atari included a mouse acclerator accessory with the Falcon.

[calimero]

Really expecting it in machine designed in 1984 ? It was made to be usable on regular televisions. What dictated border, frequencies and even max resolution. And ST added on it monochrome mode for serious work, in time were monitors were expensive. Another limiting factor was RAM - that's why max 16 colors. They could add more colors at price of slower work. That happened with TT and Falcon. End of story.

 

 

TT always work at same speed regardless of resolution, right?

 

Falcon is one that speed is affected by resolution and color numbers.

[ParanoidLittleMan]

 

 

TT always work at same speed regardless of resolution, right?

 

Falcon is one that speed is affected by resolution and color numbers.

No, TT can slowdown too in higher res. and color modes. That's the reason why SW works faster from Fast RAM, which is not shared with video. Actually, TT and Falcon have approx. same video bandwith - first has wider bus, second has faster RAM chips.

And to add that in case of ST there is actually some 'engineering' reason: Video clock is synchronized with CPU clock, so in all video modes reading video from common RAM goes at same speed. In low res, 16 color mode 2x more data is needed than in med. res for 1 pixel. and because res. is half - reading speed is same. In high res there is 640px width too, as in med, but it is drawn at double speed - what makes possible ergonomic 70 Hz refresh rate. Syncing makes possible work without CPU slowdown, well - not 100%, in some rarer cases there is little wait.

But it is true that some overscan would be good in original design. And a lot of other things. Just remember that it's made by humans in limited time.

[Thorsten Günther]

Why exactly aren't there more variety in resolution/color options on the ST?

 

Was the ST Shifter chip simply too limited? Would there have been relatively easy changes that would have enabled some customization of resolutions?

 

I know there are overscan techniques, ways of getting more colors per line -- but why not actual fundamental and native different resolutions?

 

There was a simple hardware modification to the ST called (Autoswitch) Overscan or (Auto) Lacescan that provided custom screen resolutions. I have no idea why Atari didn't incorporate this into the GSTSHIFTER when developing the STE models or why they didn't add a 160x200 pixel 256 colour mode, though.

[Xebec]

 

There was a simple hardware modification to the ST called (Autoswitch) Overscan or (Auto) Lacescan that provided custom screen resolutions. I have no idea why Atari didn't incorporate this into the GSTSHIFTER when developing the STE models or why they didn't add a 160x200 pixel 256 colour mode, though.

 

Very interesting on the mods. I will have to look into these for curiosity.

 

and I agree on the higher color mode, the 16 color mode felt limited after starting life with an Atari 800.

 

If I had to guess on the original ST 160x200 pixel/64-256 color mode though it probably has to do with the machine being intended as a business machine, and a desire to run everything under TOS (at least in concept). I really did learn to enjoy the 640x400 70hz mono though..

 

Good question on the STE.

Edited March 17, 2018 by Xebec

[Goochman]

There was a desktop ACC that allowed you to pick 'any resolution' and it would scroll the screen with the mouse. It didnt really change the resolution if you somehow managed to connect a higher rez monitor, but it was a simple software solution to allow you to have a bigger desktop area to move around. Forgot the name of it.

[ParanoidLittleMan]

There was a desktop ACC that allowed you to pick 'any resolution' and it would scroll the screen with the mouse. It didnt really change the resolution if you somehow managed to connect a higher rez monitor, but it was a simple software solution to allow you to have a bigger desktop area to move around. Forgot the name of it.

It was one of solutions for running monochrome SW on color monitor/TV. Called mono-emulator. There were 2 types - 1 with res 640x200, where 2 adjacent vertical lines were averaged, and mentioned scrollable, with virtual res. of 640x400 . But all it has nothing with HW video modes. It simply worked in ST medium res.

[MrMaddog]

There was a desktop ACC that allowed you to pick 'any resolution' and it would scroll the screen with the mouse. It didnt really change the resolution if you somehow managed to connect a higher rez monitor, but it was a simple software solution to allow you to have a bigger desktop area to move around. Forgot the name of it.

 

I've heard of it, it was called MonSTer. Read about it in a Current notes article once, that's good if you want a larger virtual desktop if you're stuck with the smaller ST video modes.

 

 

It was one of solutions for running monochrome SW on color monitor/TV. Called mono-emulator. There were 2 types - 1 with res 640x200, where 2 adjacent vertical lines were averaged, and mentioned scrollable, with virtual res. of 640x400 . But all it has nothing with HW video modes. It simply worked in ST medium res.

 

Isn't that just emulating the high res mode on a color monitor? That's what Sebra does...

[Goochman]

It was one of solutions for running monochrome SW on color monitor/TV. Called mono-emulator. There were 2 types - 1 with res 640x200, where 2 adjacent vertical lines were averaged, and mentioned scrollable, with virtual res. of 640x400 . But all it has nothing with HW video modes. It simply worked in ST medium res.

 

That wasnt it - you could pick almost any virtual size you wanted - 1024x768, etc... It didnt emulate mono on the color monitor.

[calimero]

 

That wasnt it - you could pick almost any virtual size you wanted - 1024x768, etc... It didnt emulate mono on the color monitor.

 

 

I remember that program but I can not remember it's name - it did not change resolution but allow to scroll around on virtual desktop of e.g. 1280x960. It also use STe hardware scroll.

 

 

Here you have Sebra: http://milan.kovac.cc/atari/software/index.php?folder=/OS/XTNSION/_SCREEN#SEBRA.FTP

[ParanoidLittleMan]

 

That wasnt it - you could pick almost any virtual size you wanted - 1024x768, etc... It didnt emulate mono on the color monitor.

OK. Now I remember that tried it in that time. Thanx to evil PC, now I don't need it

[Fadest]

Bigscreen used to create a virtual screen.

You can find v2 (which use STE hardscroll) in this topic :

http://www.atari-forum.com/viewtopic.php?t=28653

[calimero]

OK. Now I remember that tried it in that time. Thanx to evil PC, now I don't need it

 

 

...I must replay - Thanks to Microsoft PC now we live in a world created in Bill Gates image. It's a world founded on treachery, deceit, and most of all: naïveté of a public!

 

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[ParanoidLittleMan]

Today PC is not done by M$. It's done mostly in Taiwan. Most is manufactured in China - where they use rather own OS instead Windows.

[leech]

On 3/17/2018 at 5:42 AM, Xebec said:

 

Very interesting on the mods. I will have to look into these for curiosity.

 

and I agree on the higher color mode, the 16 color mode felt limited after starting life with an Atari 800.

 

If I had to guess on the original ST 160x200 pixel/64-256 color mode though it probably has to do with the machine being intended as a business machine, and a desire to run everything under TOS (at least in concept). I really did learn to enjoy the 640x400 70hz mono though..

 

Good question on the STE.

Quoting an old post and all that, but I always assumed they did it to try to retain more compatibility with the Atari ST.  Same reason the Mega STe would boot into 8mhz instead of 16mhz mode.

 

I also always assumed that the Amiga being able to support more resolutions was due to it's split early on of Fast vs Chip RAM, where all the video was held into the 1 or 2mb of CHIP RAM, but you could for the most part upgrade with Fast RAM to get more applications going.  That wasn't really supported on the ST line until the TT/Falcon.

[Xebec]

On 5/31/2023 at 4:11 PM, leech said:

Quoting an old post and all that, but I always assumed they did it to try to retain more compatibility with the Atari ST.  Same reason the Mega STe would boot into 8mhz instead of 16mhz mode.

 

I also always assumed that the Amiga being able to support more resolutions was due to it's split early on of Fast vs Chip RAM, where all the video was held into the 1 or 2mb of CHIP RAM, but you could for the most part upgrade with Fast RAM to get more applications going.  That wasn't really supported on the ST line until the TT/Falcon.

Others can correct me, but I think the chip vs. fast RAM isn't why the Amiga could do much more resolution or had resolution options -- it was due to the flexibility of it's chipset vs. what the ST had.

 

ST is limited to resolutions / color depths that fit within the 32KB space, while the Amiga chipset allowed the graphics portion to go up to 512KB of access (later revised upward).   Beyond that the Amiga also had circuits in the chips that allowed you to create custom modes and I'm assuming a better DAC for output/monitor flexibility.     In short, the ST "Shifter" chip is limited in flexibility and output compared to the Amiga "Denise" chip.  

 

(FWIW -- The ST chipset can actually access the full RAM space that the 68000 can, 16 MB..    while the Amiga never got above 2 MB of chipRAM.   On an ST upgraded with a 68020 and 32MB of ram (For example), you'll end up with 14/16MB of "ST ram" and 16MB of "TT Ram".  The TT Ram is exactly like Fast RAM - only accessible by the CPU).  

 

...

 

Looking at the Shifter chip info here:  https://www.synacktiv.com/ressources/Atari-ST-Internals.pdf    it looks like ST Shifter has 16 palette registers, 1 for each color -- and that's what limits the maximum color output to 16 colors at one time, without doing special tricks.  A lower resolution with more colors would have required a different chip design.

 

 

Edited June 26 by Xebec