TT/(STE) reserved screen modes

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mrbombermillzy
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TT/(STE) reserved screen modes

Postby mrbombermillzy » Tue Nov 14, 2017 7:00 pm

It seems like the Falcon and STE get most of the love around here. :lol: So...

Having recently aquired an 'unusual' TT (no audio out sockets, no VME slot 8O and a custom TOS ROM set), Ive been looking into what can be done with the TT shifter...

Apparently, no horizontal hardware scroll it seems.

Anyhow, I had a little play around with the 'RESERVED' videomodes (bits set to 3 and 5 in the Shifter TT resolution register) and whilst I could get a display, it was very strange and illogical, not conforming to any bitplane/16 pixel line length combination that I could think of.

At first I was dreaming that these modes may have been some sort of broken C2P mode left in, but unfortunately no.

It seems mode 3 is a high colour mode (8bpp?) and mode 5 something like 2bpp, although I cant get a proper bitplane count as it acts weird.

Has anyone had a good look into this (even on another shifter (STE?)) so I can be sure if Im wasting time continuing down this line of experimenting?

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Re: TT/(STE) reserved screen modes

Postby Cyprian » Tue Nov 14, 2017 9:58 pm

sounds very interesting.
what do you mean by "'RESERVED' videomodes"? is it a hardware register?
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Re: TT/(STE) reserved screen modes

Postby lp » Wed Nov 15, 2017 2:38 am

The TT has a 256 color gray scale mode and smear mode.

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Re: TT/(STE) reserved screen modes

Postby mikro » Wed Nov 15, 2017 5:37 am

Well, start with http://alive.atari.org/alive6/tt.php and if you feel there's more to research, go for it! ;-)

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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Wed Nov 15, 2017 8:51 am

I find it very strange that someone talks about "reserved" screen modes, but " no horizontal hardware scroll it seems." - :D
What about looking some specs of those computers, their video circuits ?
TT has 8bpp mode(s), and high color is 16bpp. Experimenting is good, but should first look mentioned and clarify some basic things.
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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Wed Nov 15, 2017 7:02 pm

Cyprian wrote:sounds very interesting.
what do you mean by "'RESERVED' videomodes"? is it a hardware register?


With the ST/E, the video resolutions at $ff8260 are set with the 2 bits: 00=low res, 01=med res, 10=high res, so there is a 'reserved'/unused/whatever setting: 11

The TT shifter can display more modes than the ST/E and non ST/E compatible modes are set at $ff8262. Again, not all bit positions are 'proper' modes, so there are 2 undocumented video resolutions.

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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Wed Nov 15, 2017 7:07 pm

@Mikro: Already been there. :)

Ive read all the Alive Shifter docs (vol. 1-3), Atari compendium and various others.

Unfortunately, most of the TT documentation I find is mainly based on what the ST/E does and in some cases is definitely not correct.

The most useful stuff Ive found specifically for the TT has been from Ray at TSCC, especially his new C2P truecolour mode demo.

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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Wed Nov 15, 2017 7:11 pm

@Atarizoll: Not really sure what you mean. I do intend to explore other avenues with the TT graphics like attempting horizontal overscan and scrolling at some point, but one thing at a time. :)

I was simply trying to ascertain wether something could be done with the unused videomodes mentioned in the first post.

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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Wed Nov 15, 2017 7:37 pm

Oh dear God. " so there is a 'reserved'/unused/whatever setting: 11" . And if that 11 would be of some use, somebody already would discover it in last 28 years.
"so there are 2 undocumented video resolutions." - I don't think that there is any valid, working undocumented video resolution in TT too. Your logic is just wrong. Video chips are rather complex devices, and they are designed to work in specific modes, where lot if things must cowork well. That some new mode will work by some accident is just not possible.

There is no HW supported scrolling on TT. I'm sure that designers just reasoned like: it will be not used by gamers, so we don't need HW scroll. + CPU is fast enough to do it self. Same reasoning was when they decided to not put blitter in TT. And I actually tested it in practice. Yes, TT can do fine scroll in games by using only CPU.
http://atari.8bitchip.info/SCRSH/greatgs.html
I tried that scroll actually first with Hard 'n' Heavy, but that game just works not on TT from some reason.
However, overscan may be possible on TT .
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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Wed Nov 15, 2017 8:02 pm

@Atarizoll: My logic is wrong? I asked if anyone had looked into this rather than I dont know why its not working, but nevermind :)

However, in defence of my inquisitivity, Im sure that theres LOTS of examples (try the demoscene for a start) where these 'accidental' or undocumented settings get a new result and use in the latest and greatest demos.

As for scrolling, I had come to the conclusion that smooth scrolling would have to be bit rotated by the CPU (much like the STFM).

Offtopic: I tried your Hard 'n' Heavy test scroll program for the TT and got the same results as the posted ones (by mpatton?) However, I tried turning the cache off and the colours stayed intact (the scrolling was the same though). The lines were actually scrolling, but each raster was moving out of sync to the one above. I think this may be fixable!

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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Wed Nov 15, 2017 8:56 pm

Demos use lot of diverse tricks to achieve some nice things, but I don't think that they use any new video modes.
Same can be said for Spectrum 512 and similar high-color displaying solutions. It is simply not some new video mode when you need to constantly change palette on fly, in accurate moments, to change vertical freq. and similar things. All it is achieved by heavy CPU load. While video modes don't load CPU. Higher resolutions, color modes may slow it (RAM access wait) .
Sorry, but your initial post did not say anything about CPU based (rotating, shift instructions), just mentioned that "apparently no ..." . What everyone who looked into TT specs know. ST CPU is just too slow to achieve smooth scrolling on larger screen area. Unlike much faster TT (which CPU has much faster barell shifter, even on same clock). Of course, there are some games, and I guess some demos too, which have good scroll on STs, but that's achieved mostly by using preshifted tiles and sprites.
Hard 'n' Heavy works not on TT because scrolling problems, there is something else, and game even starts not. It was just that I did code for shifting with CPU first for that game - what was used for preshift in ST versions. Then I just modded it (separate code for all 1-15 bit shifts) little for TT, which can do all it on fly, without preshift. It works fine with Giana.
I did not have TT anymore to test HnH, just got reports that original, unmodded game and that scroll v. work not at all on TT. Now I'm little confused. I usually set caches off on TT before game start.
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Re: TT/(STE) reserved screen modes

Postby troed » Wed Nov 15, 2017 9:21 pm

mrbombermillzy wrote:My logic is wrong?


It's not - have at it :) New things can be discovered also 28 years later.

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Re: TT/(STE) reserved screen modes

Postby edingacic » Thu Nov 16, 2017 1:00 am

Would it be possible to speed up scrolling in Cubase Arrange window on TT030 in high res mono? That is one area where Cubase is slow, when you have lots of tracks in arrange window and you you are zoomed in all the way and the song is playing when it reaches the edge to scroll sideways there is a little delay refresh it is ok but not smooth as we are used to in modern computers. Playing backwards is 2-3 times slower is there a reason for this?

I am using it with Nvidi 5 and it helps a lot!

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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Thu Nov 16, 2017 9:34 am

As I see, this thread turning in some chaos. Really, what speed-up of Cubase has with topic ? That's pure SW thing, so should go in APP section.
Now, some may say what Hard 'n' Heavy has with topic ? I say it has, because of mentioned scrolling on TT .
I just tried to point on what is screen mode, and what is: special tricks to achieve some visuals not possible with pure regular screen modes. There is lot of it discovered with ST, STE - and used in overscan, hi-color modes, some special hacks with blitter and probably more. So, yes, it may be that some things can still be discovered. However, nothing of it is screen mode. And I'm sure that there is no any reserved screen mode with ST, STE, TT .
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Re: TT/(STE) reserved screen modes

Postby shoggoth » Thu Nov 16, 2017 10:22 am

AtariZoll wrote:As I see, this thread turning in some chaos. Really, what speed-up of Cubase has with topic ? That's pure SW thing, so should go in APP section.
Now, some may say what Hard 'n' Heavy has with topic ? I say it has, because of mentioned scrolling on TT .
I just tried to point on what is screen mode, and what is: special tricks to achieve some visuals not possible with pure regular screen modes. There is lot of it discovered with ST, STE - and used in overscan, hi-color modes, some special hacks with blitter and probably more. So, yes, it may be that some things can still be discovered. However, nothing of it is screen mode. And I'm sure that there is no any reserved screen mode with ST, STE, TT .


@AtariZoll: This is nit picking, and there's no need to prove that you know stuff - because we all know that you know stuff. Do try to be a bit more friendly instead.

@edingacic: AtariZoll has a point, that's way off topic. Start a thread about tips & tricks around Cubase if needed.
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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Thu Nov 16, 2017 11:16 am

More nit picking: it is not enough that (some) people know that I know some stuff, forum is right place to share knowledge, experiences.
We need to use clear terminology. And that may require some talk, discussion.
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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Thu Nov 16, 2017 7:05 pm

Phew!

Its a bit of a storm in a teacup here! I came back from work and its all over the place in this post! lol

I am fully aware of what Atarizoll has done and can do...

..and I HAVE at least done a fair bit of reading and have a fairly good grasp of the TT shifter, although I havent got to the stage of counting cycles for timing yet.

However, I have NEVER read ANYWHERE anyone looking into the unused STE/TT shifter modes and telling us not to bother with them. I thought it might at least be worth a shot. They definitely work to some extent. Maybe they can be made useful? The Amiga devs managed it with HAM :lol:

I would also like to think that Atarizoll is NOT actually angry with me about asking questions :)

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Re: TT/(STE) reserved screen modes

Postby Cyprian » Thu Nov 16, 2017 8:26 pm

Guys, pls don't steal mrbombermillzy thread.

mrbombermillzy can you post any test program or a source code? I could check that on my TT
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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Thu Nov 16, 2017 8:35 pm

@Cyprian: Of course :) I dont have much time ATM, but I will post back tomorrow evening with more details including an assembly source code demo and some of my thoughts, including screen pictures!

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Re: TT/(STE) reserved screen modes

Postby AtariZoll » Thu Nov 16, 2017 10:10 pm

Folks, do you realize how ridiculous this is ? "be a bit more friendly instead" , " don't steal mrbombermillzy thread" , "telling us not to bother with them" ... I did not know that forum is place where opening some thread is like performing some show. And that OP should have some special rights.
I never said that not to bother. I explained what I consider video mode. Not to mention that saying to someone that is wrong has nothing with being friendly. There is so much things mixed up here, in technique and in human relations.
And I think that I will just say some arguments more (that would be what people should do more in discussions), and move away from this thread. Maybe if I would have TT, could be more interested and even contribute, but no TT, and actually no time too to go deeper in this.

So, we have repeated words as "reserved" and "unused" video modes here. This is what bothered me from first moment. According to OP, every bit combination in video mode register should have some valid mode. And that's the crucial word: valid. In literature often they just say that it is invalid, and results are unpredictable. For instance in opcodes of some CPU. There are 2 bits for setting video mode of ST(E), so we must have 4 video modes ? No, designers did 3 video modes, and period. Now, I''m not saying that invalid combination may not result in something, but that is just not reserved mode, and especially not unused. It would be reserved if designers planned some 4th video mode for ST. But there is nothing about it as I know.
Actually, Atari ST line design is not known about well thought reservations (to say so).
1st example: location of TOS ROM - they provided only 192 KB space for ROM in ST design - 4 years later they were forced to move ROM start to different, lower address, so 256 KB ROM can fit. Fortunately, they moved it down much more, so was no more moving in case of TT and Falcon. You always can learn something ...
Even 'better' case is:
2nd example: ST has 512 colors, and that means 9 bits, 3-3-3 bits for each basic color. What means that need 2 bytes. And they defined bit layout so, that bits 0-2 in each of first 3 nibbles are used, what is good, of course. Until design of STE with 4096 colors, so 12 bits for . And they solved adding 1 new bit for each basic color (RGB) so, to maintain compatibility in max possible extent. But bit order is just wrong - bit 3 is actually less significant, while it should be bit 0, of course. This is certain indicator that there was no any reserve made in ST shifter for future expansions.
Furthermore, whole design of ST video stage is done with not slowing CPU by video stage in mind. Adding some new mode with more res, more colors at once on screen would need complete new shifter design, and more: new MMU too.

Well, good luck in exploring TT's video stage. It may be that you really find something usable. But I will never call it 'reserved' mode. I guess that who did not get so far why, will never get it :D
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Re: TT/(STE) reserved screen modes

Postby Frank B » Fri Nov 17, 2017 8:43 am

troed wrote:
mrbombermillzy wrote:My logic is wrong?


It's not - have at it :) New things can be discovered also 28 years later.


True dat!

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Re: TT/(STE) reserved screen modes

Postby mrbombermillzy » Sat Nov 18, 2017 8:30 pm

Im a bit later than I was expecting back to this party folks. Didnt get any TT time yesterday :)

@Troed and FrankB: Thanks for the words of encouragement; I never dreamt that this enquiry was going to upset anyone here!

..and just for the record for those concerned, the word RESERVED was from the official Atari literature for these modes.

@Cyprian: Ok, so here is some sorce code, some pictures (that doesnt really explain much, but at least they show whats going on) and a brief explanation below:

TTMODEMO.zip


Mode301.JPG


Mode302.JPG


Right, so basically, Im seting TTshifter video mode at $ff8262 with the following bitmask: 0000001100000000

Then Im setting some palette colours and drawing a 16 pixel line. Have tried both 4 bpp and 8bpp.

The included program (Ive included both .prg and .s for convenience) can move the line in 4 directions with A,D,K,M. It will also leave a 'trail' or basically the previous contents. This helps me see what colours are being displayed and more importantly, if they are in the corect position.

Unfortunately, I ripped out the clean Gemdos restore routines when I was tidying up so you'll have to reset after use! Sorry! :mrgreen:

Anyhow, Im not 100% sure what is happening, but its along the lines of:

Adding more than 4bplanes adds an extra 16 pixels to the continuous line (as would be expected on a 4bpp mode) BUT it also ADDS extra colour information to the first 16 pixel set! (PICTURE 1)
Also, (I cant remember the exact details as it was 2 weeks ago now) I managed to move the bar 1 place to the right and it still kept moving the previous 16 pixel block when moving up and down. Another move to the right would 'lose' the leftmost 16 pixels after that.(PICTURE 2)

Maybe its better to look at the code and maybe set up the palette with some primary colours on bits 1,2,4,8,16,32,64,128 and set them in different combinations.

Try 4bp single (16px) row, then try 5/6/7/8bp single (16px) row and go from there.

Hope this all makes sense. If not, look at the code (I do some really thorough documenting there, and I may have forgotten some exact details here, but it will definitely be correct in there!) and let me know what you think.
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