The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby czietz » Fri Aug 03, 2018 4:32 pm

... and:
160 x 400 (16 colors out of 512),
1280 x 200 (mono, untested because I don't have a suitable monitor),

although for these two the aspect ratio will surely limit their usability.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Fri Aug 03, 2018 5:38 pm

160x400x16 (512) also, but only STs connected to multisync capable monitors will display all of them.

(and with a special adapter, the 1280x200x2 (b/w) will, really, make for some awesome demo effects. One word will turn the equivalent of a 4 low-res pixel wide "pixel" on/off. And they can be dithered to create a bunch of convincing grayscales)

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Fri Aug 03, 2018 5:40 pm

czietz wrote:1280 x 200 (mono, untested because I don't have a suitable monitor)


You have a mono/color selectable VGA switch right? Enter the mode and then flick the switch while connected to the same monitor as you use for regular ST resolutions.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby czietz » Fri Aug 03, 2018 6:04 pm

troed wrote:You have a mono/color selectable VGA switch right? Enter the mode and then flick the switch while connected to the same monitor as you use for regular ST resolutions.


Actually, I have neither a switchable VGA adapter nor a VGA monitor capable of 15 kHz timing, and that's precisely the problem. I could of course make my SCART cable (that I use on my TV for color display) switchable to mono, but no...

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Fri Aug 03, 2018 6:31 pm

czietz wrote:Actually, I have neither a switchable VGA adapter nor a VGA monitor capable of 15 kHz timing, and that's precisely the problem. I could of course make my SCART cable (that I use on my TV for color display) switchable to mono, but no...


Sorry, I confused evil's posting about mcswitch with yours. I'm back in 1.5 weeks and will surely play around with this if no one has beaten me to it by then.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby mlynn1974 » Fri Aug 03, 2018 9:56 pm

This is all very cool. I'll have to buy an ST to VGA cable to try this out.
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby ijor » Sat Aug 04, 2018 1:35 am

troed wrote:Well running GLUE in color during active display should work, right? Still only two changes per scanline.


I'm not so sure. If you run GLUE in mono at the border, but in color during the whole active display, it might interfere with the normal GLUE video state machine and it might provoke unwanted SYNC or DE edges. Furthermore, if that would work, then you wouldn't need to use the special $FF8261 address. You could run both GLUE and SHIFTER in mono at the borders, and both at color during the display. But certainly worth trying ...

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby AtariCrypt » Sat Aug 04, 2018 9:09 am

This thread is mind-blowing!! I remember my Am1ga friends back in the day laughing that we only had two colour resolutions - which couldn't be tinkered with. Of course, there are programs to interlace/scroll/use the bottom border -and all in GEM too, but I never imagined TOS had something extra hidden!! Why hide this??? Anyhow, to think something like these quirky resolutions have been lurking in the dark... Wow!!

I'm on the STe here but I've an ST also and would love to try this somehow. Perhaps an ACC/PRG for us that aren't techies?? :)

Exciting times!

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby Smonson » Sat Aug 04, 2018 9:24 am

AtariCrypt wrote:I never imagined TOS had something extra hidden!! Why hide this???


It's not really an additional mode that was intentionally hidden. It's a case of using the existing video modes in a new way (the machine is in hi-res video mode, but the shifter is interpreting the data as medium-res).

Back when the ST came out there wouldn't have been a way to see this screen mode because there was no 31KHz colour monitor available for the ST.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby tin » Sat Aug 04, 2018 12:23 pm

This is something I patched right after czietz revealed this:

http://absencehq.de/atari/newrez_prealpha.zip

I hoped to give it a thorough testing, but with the weather and all - it's your turn ;-)

This is a patched version of (or rather horribly hacked version of the horribly hacked) Overscan 1.6, that usually is a driver for HW overscan resolutions.
Now it is a driver for the new 320x400x4@72Hz resolution.
As czietz said: 160x400x16@72Hz is too small for the desktop, so it isn't included (but can be easily enabled in the source).
Not tested at all - seriously.
Image
Put this in your AUTO... wait!
This can't be said enough: This Won't Wor'k With Your Normal SCART or RGB Monitor! It'll DAMAGE It.
It really will.
You have to have a 31kHz capable screen (e.g. a VGA TFT or an multisync monitor) and the appropriate VGA switch.
Those "mono screen on vga" cables won't work either, as they don't connect the RGB signals, only mono.
Read the readme.txt.

There is also a sorry attempt to enable the 1280x200x2@50 Hz mode in there, but it bombs and this is laying around since because of that.
Overscan 1.6 isn't a good driver to begin with (TOS 1.02 and 1.04 only), but it's the only source I could find in all the minutes I spend looking :)

And obviously this only works on ST, NOT STe.

Have fun, source included, remember, horrible, horrible, horrible hack. Someone with even the first clue of AES/VDI is welcome to do a better one.
Or send me compilable sources of newer Overscan or of a Lacescan version.

Tested with the following VGA RGB capable adapters:
http://centuriontech.eu/product/st2vga-black/
https://www.exxoshost.co.uk/atari/last/storenew/#0107
Not tested, but should work:
https://goo.gl/FuSp1X (mcswitch)
https://goo.gl/1hBBSv

[EDIT: forgot the photographic evidence, added some clarifications, removed typos]
Last edited by tin on Sun Aug 05, 2018 12:36 pm, edited 5 times in total.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby tin » Sat Aug 04, 2018 1:15 pm

czietz wrote:... and:
1280 x 200 (mono, untested because I don't have a suitable monitor),


For the record: this mode (1280x200x2@50Hz) works fine with an NEC1970NXp, centurion/ubeswitch tested. This even worked in the NewRez Desktop driver, but with the mono font, so it looked more like 1280x100, aka totally unsuable :/

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby BlankVector » Sat Aug 04, 2018 5:59 pm

tin wrote:This is a patched version of (or rather horribly hacked version of the horribly hacked) Overscan 1.6, that usually is a driver for HW overscan resolutions.

Excellent :D
Really, great progress in this thread.
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby calimero » Sun Aug 05, 2018 3:10 am

tin wrote:
czietz wrote:... and:
1280 x 200 (mono, untested because I don't have a suitable monitor),


For the record: this mode (1280x200x2@50Hz) works fine with an NEC1970NXp, centurion/ubeswitch tested. This even worked in the NewRez Desktop driver, but with the mono font, so it looked more like 1280x100, aka totally unsuable :/

Xex... Cool. 1280 x 200 is 4.8 times lower then 1280 x 960 - a TT reaolution.
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby ube » Sun Aug 05, 2018 3:14 pm

tin wrote:For the record: this mode (1280x200x2@50Hz) works fine with an NEC1970NXp, centurion/ubeswitch tested. This even worked in the NewRez Desktop driver, but with the mono font, so it looked more like 1280x100, aka totally unsuable :/


Wait, what? Did you really use an ubeswitch with auto detection of mode?

I haven't looked into this too much, but I'm doing vsync pulse width detection for choosing what to output, could it be that the P/W does not change in this mode?
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby tin » Mon Aug 06, 2018 10:17 am

ube wrote:
tin wrote:For the record: this mode (1280x200x2@50Hz) works fine with an NEC1970NXp, centurion/ubeswitch tested. This even worked in the NewRez Desktop driver, but with the mono font, so it looked more like 1280x100, aka totally unsuable :/


Wait, what? Did you really use an ubeswitch with auto detection of mode?

I haven't looked into this too much, but I'm doing vsync pulse width detection for choosing what to output, could it be that the P/W does not change in this mode?


I sure did use the ubeswitch. In my little testbed App (with the whole system & IRQs killed) I have to press the knob to force it to show the mono line, though.
The 1280x200 mode outputs 50Hz timing but sends pixel data via mono line, as opposed to the 160/320x400, which send a 72Hz timing but pixel data via rgb lines.

Edit: 160/320x400, not 200:)
Last edited by tin on Tue Aug 07, 2018 9:48 pm, edited 1 time in total.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby tteclado » Mon Aug 06, 2018 11:46 am

I am hoping to try, the software of some guru, of the Videl Inside type in the ST (maybe Shifter Inside?) :lol:

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby leech » Wed Aug 08, 2018 11:29 pm

Curious, could something be tricked into using this in 640x200(Medium Resolution) but tricking it to Mono for 31khz? Thus eliminating the need for Monitors that support 15khz?
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby Smonson » Thu Aug 09, 2018 3:21 am

leech wrote:Curious, could something be tricked into using this in 640x200(Medium Resolution) but tricking it to Mono for 31khz? Thus eliminating the need for Monitors that support 15khz?

If it's 200 colour lines, then it'll only be 15KHz. The 400 mono lines are faster because they only have half the amount of data on each line compared to low and medium. If there was a 320x400x4 mode, it'd be a different story.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby leech » Thu Aug 09, 2018 4:27 am

"Unlocking the secrets of the ST: 33 years at a time." Alternate thread title.
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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby nobox » Thu Aug 09, 2018 9:15 am

On an STFM, this should work with a (modified) SM124, too

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Thu Aug 09, 2018 9:41 am

So while not as awesome as this trick, since it requires an extensive hardware upgrade, some of you might recall the doubleST video modes I documented here: https://blog.troed.se/projects/atari-st ... deo-modes/

Combining that upgrade with this trick will result in:

320x400x16
640x400x4

(and 2560x200x2, but let's just forget how ludicrous that would be;))

Unfortunately, there are no vertical borders that can be opened with the GLUE in high res so the tantalizing 640x480x4 cannot be done.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby nobox » Thu Aug 09, 2018 9:59 am

640x400 with 4 shades of gray with a 16 MHz STFM would be exiting , i think ...

@troed: Could you try to use your modified 1040 STFM and combine it with my SM124 modification

https://forum.atari-home.de/index.php?topic=12245.0

and with this trick ?

Should result in 320x400 in 16 shades of grey
or 640x400 in 4 shades

on a SM124 without any graphic card ...

Of course, you should use pin 2 instead of 11 for the video signal, as far as I understand it ...

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby Smonson » Thu Aug 09, 2018 10:53 am

...I take back what I said about 320x200x256 being impossible.

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Thu Aug 09, 2018 2:43 pm

Smonson wrote:...I take back what I said about 320x200x256 being impossible.


_With_ your Shifter re-impl ;)

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Re: The SECRET VIDEO MODE in an ST: 400 lines in COLOR (and with 72 Hz)!

Postby troed » Thu Aug 09, 2018 2:46 pm

nobox wrote:@troed: Could you try to use your modified 1040 STFM and combine it with my SM124 modification


I only have non-working SM124s I haven't fault analyzed yet. Will run those modes in color on my flatscreens :)

(My doubleST machine runs off a GAL controlled clock divider nowadays and can easily switch between all modes)


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